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FRONTISPIECE 


Lassen  Peak  in  1900.  View  from  Manzanita  Lake  looking  southeast. 


THE 


VOLCANIC  ACTIVITY  AND  HOT 
SPRINGS  OF  LASSEN  PEAK. 


BY 

ARTHUR  L.  DAY  AND  E.  T.  ALLEN. 


THE  UBHRK!  Bf  (Hf 

MAY  1 1  1S25 

UN1VEKSITY  9F  ILUIWIS 

Published  by  the  Carnegie  Institution  of  Washington 
Washington,  April,  1925 


CARNEGIE  INSTITUTION  OF  WASHINGTON 
Publication  No.  360 


PREFACE 


The  Geophysical  Laboratory  was  first  attracted  to  the  study  of  Lassen  Peak 
by  Mr.  J.  S.  Diller,  Geologist  of  the  U.  S.  Geological  Survey.  Mr.  Diller  was  on 
the  ground  during  the  early  eruptions  of  1914  and  on  his  return  to  Washington 
expressed  a  wish  that  the  Geophysical  Laboratory  should  cooperate  in  the  study  of 
the  outbreak  because  of  the  physical  and  chemical  relations  involved.  It  was 
agreed,  tentatively,  that  the  Geological  Survey  would  undertake  the  necessary 
geological  studies1  and  the  Geophysical  Laboratory  the  physical  and  chemical 
phenomena.  Accordingly  the  authors  made  their  first  visit  to  the  mountain  in 
June,  1915,  some  four  weeks  after  the  culminating  volcanic  outbreak  of  that  year. 
Except  insofar  as  conclusions  could  be  drawn  from  the  visible  consequences  of  the 
eruptive  activity  of  the  first  year  (1914)  and  the  great  catastrophic  outbreak  of 
May  19-22,  1915,  we  were  therefore  dependent  upon  others  for  many  of  the  field 
observations. 

We  are  accordingly  under  obligation  first  of  all  to  Mr.  J.  S.  Diller,  of  the  U.  S. 
Geological  Survey,  who  visited  the  Mountain  in  1914,  1915  and  1921,  and  cooper¬ 
ated  with  us  throughout,  theft  to  the  Supervisors  and  Rangers  of  the  Forest  Service 
who,  although  inexperienced  in  volcanic  matters,  were  nevertheless  men  practiced 
in  field  observation,  of  excellent  judgment  and  keen  discrimination,  and  contributed 
very  greatly  to  the  record  contained  in  the  following  pages. 

Mr.  A.  Sifford,  Proprietor  of  the  Drakesbad  Camp  (seven  miles  southeast  of 
Lassen  Peak),  Mr.  Roy  Sifford  his  son,  and  Charley  Yori,  who  acted  as  guide  in 
this  region  during  both  1914  and  1915,  not  only  provided  all  facilities  and  much 
camp  comfort,  but  were  able  to  contribute  important  details  of  personal  observa¬ 
tion  and  photographs,  as  did  also  the  brothers  George  W.  Olsen  and  Nelson  Olsen 
of  Chester,  whose  observations  will  be  found  in  detail  in  the  Appendix  (page  176). 

We  were  also  fortunate  in  having  the  cooperation  of  Mr.  B.  E.  Loomis,  one  time 
a  professional  photographer  and  now  in  the  lumber  business  at  Viola  (7  miles  north¬ 
west  of  Lassen  Peak)  whose  splendid  collection  of  photographs,  some  of  them  copy¬ 
righted,  were  unreservedly  placed  at  our  disposal,  together  with  his  diary.  The 
frontispiece  and  many  of  the  finest  illustrations  in  this  book  are  the  work  of  Mr. 
Loomis. 

Miss  Alice  Dines,  Postmistress  at  Manton  (15  miles  west  of  Lassen  Peak)  kept 
an  unceasing  watch  upon  the  mountain  from  the  beginning  to  the  end  of  its  activity. 
Efer  observations  will  also  be  found  in  the  Appendix  (page  176). 

Of  the  occasional  visitors  the  authors  wish  particularly  to  acknowledge  the 
assistance  of  Professor  R.  S.  Holway  of  the  University  of  California,  who  permitted 
the  free  use  of  his  photographs  and  the  record  of  his  visit  in  June,  1915.  Likewise 
the  written  (and  photographic)  record  of  the  visits  of  Mr.  W.  H.  Spaulding,  Presi¬ 
dent  of  the  Great  Western  Power  Company,  and  a  group  of  friends,  in  1914  and  1915, 

1  Not  yet  published, 
iii 


5  4  $56 


IV 


and  the  photographs  of  Mr.  Jack  Robertson  of  San  Francisco  were  kindly  placed  at 
our  disposal.  The  photographers  Mr.  R.  E.  Stinson  of  Red  Bluff,  Mr.  Chester 
Mullen  of  Redding,  and  Mr.  E.  N.  Hampton  of  Mineral,  also  kindly  permitted  the 
use  of  excellent  photographs,  some  of  which  are  copyrighted. 

To  all  of  the  above  named  individuals  and  many  others  who  cannot  be  men¬ 
tioned  in  so  brief  a  space  the  authors  feel  under  great  personal  obligation  for  the 
uniform  courtesy  shown  in  helping  us  to  provide  a  complete  record  of  this  volcanic 
outbreak,  the  first  of  its  kind  in  this  country  in  our  generation. 

For  the  laboratory  studies  of  volcano  material  collected  during  the  eruptions 
the  authors  are  most  grateful  for  the  indispensible  cooperation  of  their  colleagues 
Messrs.  Aurousseau,  Merwin,  Morey  and  Shepherd,  whose  accurate  work  has 
thrown  a  flood  of  light  on  the  whole  problem  of  volcanic  activity. 

The  study  of  the  hot  springs  (Part  II)  is  entirely  the  work  of  the  authors,  with 
the  help  on  the  ground  of  Charley  Yori  and  Allen  Raker,  guides,  who  aided  in  every 
practical  way  during  the  years  1915,  1916,  1922  and  1923. 

The  Authors. 


CONTENTS. 


PAGE. 

Preface .  iii 

Illustrations .  vii 

Introduction .  i 

Part  I.  Eruption  of  Volcano. 

Chapter  I.  Sequence  of  Events .  j 

Beginning  of  explosive  activity,  1914 .  3 

Character  of  explosions  of  1914 .  10 

Culmination  of  explosive  activity  May  19  to  22,  1915 .  14 

First  appearance  of  glowing  lava .  16 

First  horizontal  blast  and  mud  flow,  May  19,  1915 . . . ' .  19 

Origin  of  the  mud  flow .  20 

Second  horizontal  blast,  May  22,  1915 .  25 

Period  of  subsidence .  26 

Summary  of  field  observations .  30 

Second  period  of  activity,  May  1915 .  33 

Chapter  II.  Chemical  and  Physical  Relations.  Laboratory  Study .  36 

Chemical  composition .  36 

Products  of  recent  activity .  40 

Water  content  of  conduit  lava .  45 

Gas  content  of  conduit  lava .  46 

Ferric  ratio  in  conduit  lava .  48 

Thermal  study  of  conduit  lava .  49 

Mineral  changes  on  heating .  49 

Bending  (flow)  temperature  of  dense  andesite .  50 

General  effects  of  heating  to  1 260°  C . : .  31 

Some  conclusions  from  laboratory  studies  of  conduit  lava .  51 

Chapter  III.  Field  Evidence  of  Temperature  Relations .  54 

Horizontal  blasts .  54 

Lava  temperature  and  “flow” .  59 

Mechanics  of  upheaval  of  plug  and  of  horizontal  blasts .  64 

Volcanic  bombs  and  breccia .  68 

Bread-crust  bombs .  69 

Chapter  IV.  Some  Inferences  Concerning  Causes  of  Activity .  72 

Part  II.  The  Hot  Springs  of  Lassen  National  Park. 

Introduction .  86 

Chapter  I.  Observations  and  Experimental  Work .  87 

Location  of  springs .  87 

Geologic  relations  of  hot  springs .  87 

Hot-spring  groups .  87 

Geyser .  88 

Boiling  Lake  or  Lake  Tartarus .  88 

Drake’s  Springs .  90 

Devil’s  Kitchen .  91 

Bumpass  Hell .  94 

Supan’s  Springs .  96 

Morgan’s  Springs .  98 

Types  of  springs .  100 

Mud  pots  and  mud  volcanoes .  101 

Chapter  II.  Field  and  Laboratory  Work .  104 

Work  in  the  field .  104 

Maps .  104 

Temperature  measurements .  104 

Other  field  tests .  108 

Tests  at  camp .  109 

Determination  of  ferrous  iron .  109 

Determination  of  free  acid .  109 

Work  in  the  laboratory .  no 

The  waters .  no 

Peculiarities  in  the  composition  of  the  waters .  no 

Reaction  of  the  waters .  113 


v 


VI 


Salt  incrustations . 

Analysis  of  the  salts . 

Determination  of  pentathionate . 

Microscopic  examination . 

The  sediments . 

The  gases . 

Collection  of  the  gases . 

Analysis  of  the  gases . 

Composition  of  the  gases . 

Chapter  III.  Chemical  Effects  of  the  Hot  Waters  and  Gases . 

Chemical  changes  in  the  springs . 

Formation  of  pyrite . 

Absence  of  marcasite . 

Origin  of  sulphuric  acid . 

Chemical  decomposition  of  the  lavas . 

Significance  of  the  occurrence  of  kaolin . 

Significance  of  the  occurrence  of  alumte . 

Silica  the  final  residue  of  rock  decomposition . 

Two  types  of  lava  decomposition  contrasted . 

Formation  of  pentathionate . 

Significance  of  hydrochloric  acid  in  the  crater  gases . 

Uniformity  of  rock  decomposition . 

Chapter  IV.  Origin  of  Hot  Springs  and  their  Relation  to  Igneous  Activity 

Source  of  heat  in  the  hot-spring  areas . 

Volcanic  heat . 

Radioactivity  as  a  source  of  heat . 

Heat  developed  from  chemical  processes . 

Heat  carried  away  by  surface  water . 

Source  of  the  water . 

Surface  water . 

Seasonal  changes  in  thermal  activity . 

Variation  in  thermal  activity  in  different  years . 

Salt  patches  as  an  indication  of  the  state  of  the  ground . 

Recent  outbreak  of  thermal  activity . 

Fluctuations  in  the  composition  of  the  waters . 

The  presence  of  magmatic  water . 

Relation  of  hot  springs  to  the  magma . 

Views  of  other  investigators . 

The  magmatic  water . 

Acid  and  alkaline  springs . 

Coexistence  of  acid  and  alkaline  springs . 

Time  relation  between  acid  and  alkaline  springs . 

Substances  of  secondary  origin  in  volcanic  hot  springs . 

The  means  by  which  heat  is  conveyed  to  the  surface . 

Conclusion . 

Appendix . 


page. 

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.  176 


ILLUSTRATIONS. 


PAGE 

Lassen  Peak  in  1900.  View  from  Manzanita  Lake  looking  southeast .  Frontispiece. 

1.  Successive  views  of  the  explosion  of  June  14,  1914,  taken  near  Manzanita  Lake .  9 

2.  Views  of  the  mud  flow,  May  19,  1915,  in  Lost  Creek  and  Hat  Creek  Valleys .  19 

3.  May  22,  1915.  Lassen  Peak  and  Lost  Creek  Valley  after  the  first  and  before  the  second  horizontal  blast .  25 

4.  July  22,  1915.  Lassen  Peak  from  the  northeast  showing  the  devastated  area  after  the  blast  of  May  22,  1915 .  26 

5.  May  27,  1916.  Same  view  as  Plate  4,  one  year  later .  28 

6.  (1)  A  part  of  the  exposed  eastern  end  of  the  volcano  plug .  62 

(2)  An  instance  of  flow  structure  in  situ  cited  by  Diller .  62 

(3)  (Center)  A  large  block  from  the  original  plug  (solid)  tilted  outward  90°  by  the  upheaval .  62 

7.  The  Geyser.  Northernmost  Pool .  88 

8.  May  19,  1916.  Boiling  Lake.  The  outlet  at  high  water .  90 

9.  May  19,  1916.  Mud  pots  on  the  shore  of  the  Boiling  Lake  (high  water) .  92 

10.  July  21,  1915.  East  end  of  the  Devil’s  Kitchen  showing  disintegration  of  the  ground  by  thermal  action .  94 

11.  July  10,  1915.  A  portion  of  Bumpass  Hell  looking  southwest .  96 

12.  July  10,  1915.  Spouting  Spring  (No.  14,  Fig.  50)  at  Bumpass  Hell .  142 

13.  (0  JUL  IO>  1915-  Deep  hot  pool  at  Bumpass  Hell  (No.  16,  Fig.  50)  nearly  filled  with  water .  157 

(2)  Same  pool  empty  July  1922.  Great  fumarole  extinct .  137 

TEXT-FIGURES. 

1.  June9,  1914.  One  of  the  earliest  eruptions  of  Lassen  Peak .  4 

2.  1891.  Inside  the  old  crater  looking  southeast .  5 

3.  The  bottom  of  the  old  crater  with  its  pool  of  water  draining  westward  through  the  western  notch .  5 

4.  The  western  notch  in  the  crater  rim  before  the  upheaval  in  May,  1915 .  6 

5.  June  28,  1914.  Explosion  crater  showing  the  “lateral  fissures” .  7 

6.  The  first  explosion  crater  showing  the  snow  with  ash  and  debris  lying  upon  it .  7 

7.  June  20,  1914.  Looking  north.  Explosion  vent  now  600  feet  long  and  100  feet  wide .  9 

8.  October  27,  1914.  The  explosion  crater  and  its  vertical  rift .  11 

9.  May  22,  1915.  1  he  great  eruption  seen  from  the  east .  15 

10.  July  20,  1915.  The  upheaval  in  the  western  notch .  18 

11.  July  14,  1915.  The  northeast  flank  of  the  mountain  where  the  horizontal  blasts  and  the  flood  originated .  21 

12.  June  4,  1915.  Logs  piled  on  the  divide  between  Lost  Creek  and  Hat  Creek .  22 

13.  July  18,  1915.  Boulders  and  tree  trunks,  Lost  Creek  Valley .  22 

14.  June  4,  1915.  Boulder  from  Lassen  Peak  carried  for  4  miles  by  the  mud  flow  of  May  19,  1915 . .  .  .  22 

15.  June  4,  1915.  Log  jam  below  Jessen  Meadow .  22 


16.  July  14,  1915.  View  across  Lost  Creek  Valley  S  to  N  showing  the  timber  lying  away  from  the  blast  and  across  the 


hillside.  In  the  foreground  the  center  of  the  path  of  the  blast  now  swept  clean .  23 

17.  June  28,  1915.  The  path  of  the  blast  showing  the  sand-blasted  trunks  on  the  south  border .  24 

18.  May  24,  1915.  Minor  mud  flows  on  the  north  and  west  flanks  of  the  mountain  due  to  falling  ash  and  condensed 

steam  melting  the  snow .  25 

19.  July  26,  1915.  The  bottom  of  the  summit  crater  after  the  great  eruption  of  May  22,  1915 .  27 

20.  July  15,  1915.  Rift  extending  radially  down  the  north  flank  of  Lassen  Peak  after  the  great  eruption  of  May  22,  1913  27 

21.  July  7,  1922.  Summit  of  Lassen  Peak.  Shallow  1917  crater .  28 

22.  Lassen  Peak  from  the  air  (northwest)  showing  all  three  summit  craters .  29 

23,24.  June  1914.  Explosions  encountered  on  the  summit  by  Robertson’s  party .  30 

25.  Explosions  in  quick  succession  in  the  summer  of  1914 .  32 

26.  August  10,  1915.  Summit  looking  west  along  the  southern  edge  of  the  upheaved  plug .  33 

27.  Curves  showing  the  variations  in  the  composition  of  the  Lassen  Peak  rocks .  38 

28.  A  prism  of  dense  Lassen  andesite,  supported  at  two  points  and  heated  to  1040°  C.  for  15  minutes .  50 

29.  April  28,  1922.  Sketch  Map  showing  a  portion  of  Lassen  Volcanic  National  Park .  55 

30.  July  7,  1913.  Green  pines  blown  down  and  charred  at  base  of  Jessen  Mountain  on  Lost  Creek,  May  22,  1915,  by  a 

hot  blast  from  Lassen  Peak .  56 

31.  June  28,  1915.  Bread-crusted  boulder  imbedded  in  the  snow  on  the  summit  showing  that  the  boulder  was  cold  when 

it  fell .  57 

32.  July  26,  1915.  View  of  the  Summit  Crater  of  Lassen  Peak  after  the  upheaval  (on  or  about  May  15,  191 5) .  60 

33.  July  15,  1915.  Another  view  of  the  upheaved  floor  of  the  crater  showing  details .  61 

34.  August  14,  1923.  Looking  west  across  the  upheaved  area  eight  years  later .  63 

35.  Another  view  looking  northwest  across  the  exposed  eastern  end  of  the  volcano  plug .  66 

36.  Pumiceous  material  containing  dacite  inclusions .  68 

37.  July  17,  1915.  Bread-crust  bomb  about  four  feet  long,  northeast  slope  of  Lassen  Peak  about  one-half  mile  from 

crater .  7° 

vii 


V1U 


TEXT  FIGURES — Continued. 

PAGE 

38.  May  22,  1915.  A  view  of  the  great  eruption  from  Mineral,  12  miles  south  of  Lassen  Peak .  73 

39,  40.  The  great  eruption  of  May  22,  1915,  viewed  from  Mineral,  12  miles  south .  74 

41.  Diagrams  showing  change  of  pressure,  temperature,  and  composition  of  the  univariant  equilibria  between  solid, 

liquid,  and  vapor  phases  in  the  binary  system  H>0-KN03 .  7$ 

42.  May  22,  1915.  View  of  the  great  eruption  from  Red  Bluff,  45  miles  southwest .  83 

43.  The  Geyser  Plumas  County.  Southernmost  pool,  July  1922 .  88 

44.  July  23,  1915.  Boiling  Lake  (Temp.  50°  C.)  surrounded  by  a  beautiful  evergreen  forest.  Outlet  (then  dry)  in  the 

foreground.  Pyrite  crystals  abundant  in  the  bed  of  the  stream .  89 

45.  May  19,  1916.  Boiling  Lake  looking  northwest.  Lassen  Peak  in  the  background .  90 

46.  May  26,  1916.  Springs  on  the  bank  of  Boiling  Lake.  Pyrite  crystals  abundant  in  the  clay  banks .  91 

47.  Sketch  Map  of  “Devil’s  Kitchen”  area,  six  miles  southeast  of  Lassen  Peak .  92 

48.  July  21,  1915.  Four  steaming  springs  at  the  foot  of  a  high  bank,  east  end  of  Devil’s  Kitchen .  93 

49.  View  of  Bumpass  Hell  (looking  west)  taken  in  1891.  Activity  greater  than  at  the  present  time .  94 

50.  July  1,  1922.  Sketch  Map  of  “Bumpass  Hell”  hot-spring  region,  Lassen  Peak,  California .  95 

51.  July  10,  1915.  Large  shallow  pool,  bright  brown  color,  considerable  gas  evolution  (center),  pyrite  scum  (right).  ...  96 

52.  July  10,  1915.  Large  sulphur  cauldron,  (No.  4,  fig.  50),  Bumpass  Hell.  No  outflow.  Little  gas .  97 

53.  July  1923.  Supan’s  Springs,  lower  group,  showing  the  effects  of  thermal  action .  98 

54.  July  1923.  Mill  Creek  Hot  Springs.  Probably  the  last  vestige  of  activity  in  the  old  Lassen  Peak  crater  southeast 

of  Brokeoff  Mountain .  99 

55.  July  10,  1915.  General  view  of  Bumpass  Hell  hot  springs,  looking  west .  100 

56.  July  10,  1915.  Large  mud  pot  in  Bumpass  Hell.  Inactive  since  1915 .  101 

57.  June,  1922.  Mud  pot  in  the  Devil’s  Kitchen  (No.  10,  fig.  47).  Bursting  gas  bubble  in  the  foreground .  102 

58.  July  1923,  Boiling  Lake.  Mud  pot  active  helow  the  lake  level  (foreground),  others  drowned.  Very  low  water.  .  .  .  102 

59.  Sketch  Map  of  the  Boiling  Lake  (Tartarus)  showing  location  of  the  springs  in  June,  1916 .  114 

60.  July  1923.  A  warm  pool  in  the  Devil’s  Kitchen  near  No.  10,  Fig.  47.  On  the  surface  floated  a  black  scum  of  finely 

divided  pyrite .  120 

61.  July  1923.  Another  view  of  sulphur  cauldron  (fig.  52)  at  Bumpass  Hell.  Greater  gas  evolution  with  lower  water 

level  (no  outlet)  and  higher  temperature .  121 

62.  July,  1923.  A  group  of  quiet  sulphur  pools  (fig.  50,  No.  15)  Bumpass  Hell .  121 

63.  May  20,  1916.  Stream  in  Devil’s  Kitchen  showing  pyrite  crystals  (dark  areas)  in  furrows  on  the  sandy  bottom 

(looking  down  through  the  water) .  122 

64.  July  2,  1915.  Hot  pools  in  the  Devil’s  Kitchen  (No.  9,  fig.  47)  showing  scums  of  pyrite  reflecting  light  like  bronze 

mirrors .  123 

65.  June  1922.  Collecting  gases  at  Bumpass  Hell.  (Spring  14,  fig.  50) .  124 

66.  June  1923.  Collecting  gases  at  the  Mud  Springs  of  Boiling  Lake .  125 

67.  Device  for  removing  the  gas  from  the  collecting  tube .  126 

68.  Pipette  for  absorbing  hydrogen  sulphide .  126 

69.  Apparatus  for  analysis  of  gases . 127 

70.  Apparatus  for  analysis  of  gases.  “Moist”  burette,  absorption  pipettes  and  combustion  pipette .  128 

71.  Apparatus  for  photographing  spectra  of  the  inert  gases .  130 

72.  June  1923.  Sulphur-bearing  pools  at  Supan’s  Springs .  140 

73.  June  1923.  Spouting  Spring  in  the  Devil’s  Kitchen  (No.  3,  fig.  47).  White  alunite  mound  in  background .  142 

74.  June  1922.  Western  half  of  pool  No.  14  Bumpass  Hell .  143 

75.  July  2,  1Q15.  Eastern  end  of  the  Devil’s  Kitchen  showing  encrusted  ground  and  sulphur  pools .  148 

76.  July  2,  1915.  Western  end  of  the  Devil’s  Kitchen  close  to  Warner  Creek .  153 

77.  June  1923.  Large  mud  pot  at  Bumpass  Hell  (fig.  50,  No.  17).  Active  at  the  bottom.  Color,  battleship  gray.  .  .  156 

78.  June  1922.  Fresh  outbreak  of  thermal  activity  in  the  Devil’s  Kitchen .  158 

79.  The  same  region  in  July  1923.  All  of  the  central  portion  of  the  picture  has  settled  8  to  10  feet .  158 

80.  May  20,  1916.  Wonderful  magenta  terraces  colored  by  oxide  of  iron.  Obliterated  by  the  new  outbreak  at  the 

Devil’s  Kitchen  (1923) .  139 

81.  June  1922.  Spouting  spring  in  Devil’s  Kitchen  (No.  23,  fig.  47).  A  jet  of  hot  water  and  steam  8  or  10  feet  in 

height .  160 


PART  I. 

ERUPTION  OF  THE  VOLCANO. 


By  Arthur  L.  Day  and  E.  T.  Allen. 


INTRODUCTION.1 


Lassen  Peak,  in  the  southeastern  corner  of  Shasta  County,  California,  is  the 
southernmost  expression  of  a  great  volcanic  region,  to  which  Mount  Shasta, 
Mount  Hood,  and  Mount  Rainier  belong.  Volcanic  activity  in  the  Lassen  region 
began  in  early  Neocene  time  and  has  continued,  with  diminishing  violence,  to  the 
present  day.  The  period  of  most  violent  activity  was  concomitant  with  the  up¬ 
heaval  of  the  Sierra  Nevada,  and  some  of  the  earlier  lavas  are  intercalated  with 
deposits  of  the  lone  epoch.  The  earliest  extrusions  were  of  hornblende  andesite, 
and  the  general  course  of  eruption  produced,  in  turn,  pyroxene  andesite,  rhyolite, 
dacite,  basalt,  and,  finally,  quartz  basalt.  In  detail  the  sequence  is  more  com¬ 
plicated,  some  of  the  basalt  flows  being  old,  but,  in  general,  they  are  the  youngest 
lavas  of  the  region.  Some  rhyolite  flows  have  succeeded  flows  of  dacite,  but  for  the 
most  part  the  former  precede  the  latter.2  The  absence  of  augite  andesite  from 
the  whole  magmatic  region  to  which  Lassen  Peak  and  the  associated  volcanoes 
belong  is  noteworthy.3  Whatever  may  have  been  the  course  of  differentiation,  that 
of  eruption  has  been  from  the  production  of  intermediate  lavas  to  that  of  extreme 
types,  ending  with  a  basic  type;  a  sequence  that  was  pointed  out  first  by  von 
Richtofen  as  that  of  Californian  and  other  lavas,4  and  later  by  Iddings,5  as  the 
general  law  of  succession  of  lavas.  The  activity  of  the  whole  comagmatic  region  of 
northern  California,  Oregon,  Washington,  and  Idaho,  has  been  so  low  within  recent 
times  that  the  field  may  be  regarded  as  almost  extinct.  Lassen  Peak  and  Cinder 
Cone,  however,  have  shown  activity  within  historic  times,6  Cinder  Cone  having 
extruded  a  flow  of  quartz  basalt,  perhaps  no  more  than  200  years  ago,  and  Mount 
St.  Helens  and  Mount  Hood  are  believed  to  have  been  the  scenes  of  ash  eruptions 
within  historic  times.7 

The  terrane  through  which  the  lavas  of  Lassen  Peak  have  been  erupted  is 
worthy  of  comment.  The  extrusions  rest  upon  the  Chico  formation  (Cretaceous)  of 
the  upper  part  of  the  Sacramento  Valley.  Beneath  the  Chico  are  the  Jura-Trias 
rocks,  which  in  turn  rest  unconformably  upon  contorted  Palaeozoic  formations. 
The  Palaeozoic  formations  contain  both  contemporaneous  volcanic  and  transgressive 
igneous  rocks  of  varied  nature,  some  of  the  volcanic  rocks,  though  metamorphosed, 
being  similar  to  those  of  the  Tertiary  eruptions,  though  they  may  bear  no  magmatic 
resemblance  to  them.  Chemically  they  are  uninvestigated.  The  thicknesses  of 
the  various  members  of  this  Palaeozoic  and  Mesozoic  terrane  are  unknown,  and 

1  By  M.  Aurousseau. 

2  J.  S.  Diller,  Lassen  Peak,  U.  S.  Geol.  Survey,  Folio  No.  15,  1895. 

3  Hague  and  Iddings,  Notes  on  the  Volcanoes  of  Northern  California,  Oregon,  and  Washington  Territories,  Amer.  Journ. 
Sci.,  (3),  25,  222-235,  1883. 

4  F.  von  Richtofen,  Principles  of  the  Natural  System  of  Volcanic  Rocks,  Mem.  California  Acad.  Sci.,  1,  39,  1868. 

5  J.  P.  Iddings,  The  Origin  of  Igneous  Rocks,  Bull.  Phil.  Soc.  Washington,  12,  178,  1892;  Igneous  Rocks,  1,  257,  1909. 

fi  A.  L.  Day,  Possible  Causes  of  the  Volcanic  Activity  at  Lassen  Peak,  Bull.  Seismol.  Soc.  America,  12,  35-46,  1922; 
fourn.  Franklin  Inst.,  194,  569-582,  1922.  J.  S.  Diller,  Lassen  Peak — our  most  active  volcano,  Bull.  Seismol.  Soc.  America  , 
6,  1-7,  1916;  A  late  volcanic  eruption  in  Northern  California,  U.  S.  Geol.  Survey,  Bull.  79,  1891. 

7  W.  R.  Jillson,  Geogr.  Rev.,  3,  481-485,  1917;  II,  398-405,  1921. 

1 


2 


though,  for  the  most  part,  they  consist  of  shales  and  sandstones,  limestones  appear 
to  be  abundant,  especially  in  the  Calaveras  formation  (Carboniferous)  and  in  the 
Cedar  formation  (Jura-Trias).1  There  are  abundant  limestones  in  the  Carboni¬ 
ferous  of  the  Klamath  Mountain  section,  one  horizon  2,000  feet  in  thickness 
outcropping  for  50  miles  along  the  McCloud  River,  50  miles  to  the  northwest  of 
Lassen  Peak.  The  Trias  of  this  district  emerges  from  beneath  the  Lassen  volcanic 
field  along  Cedar  Creek,  and  contains  one  horizon  of  limestone  200  feet  in  thickness. 
The  dip  and  strike  of  the  Palaeozoic  rocks  of  the  Klamath  Mountains  render  it  not 
improbable  that  they  extend  beneath  the  Mesozoic  formations  underlying  part,  at 
any  rate,  of  the  Lassen  volcanic  field,2  but  no  alkaline  rock,  as  possible  evidence  of 
assimilation  of  limestone  (Daly),  has  been  found  in  the  region,  with  the  possible 
exception  of  a  boulder  of  hornblende  basalt,  found  in  a  stream  bed  near  the  Great 
Bend  of  the  Pit  River  on  the  extreme  northwest  of  the  Lassen  sheet.  The  relations 
of  this  rock  are  quite  unknown,  and  it  can  hardly  be  considered  to  belong  to  the 
Lassen  suite  of  lavas.  Nothing  of  its  kind,  chemically  or  mineralogically,  is  known 
from  the  field.3 

The  position  of  the  Lassen  group  of  vents  with  relation  to  the  orography  of  the 
surrounding  regions  is  significant.  They  lie  at  the  northern  extremity  of  the 
geosynclinal  depression  of  the  Sacramento  Valley,  which  separates  the  mass  of  the 
Sierra  Nevada  from  that  of  the  Coast  Range.  The  depression  is  partly  filled  with 
the  flat-lying  Mesozoic  and  Neocene  sediments.  The  abundance  of  volcanic  vents 
between  the  northern  end  of  the  Sierra  Nevada  and  the  Klamath  Mountains  is  in 
accord  with  the  tectonic  weakness  of  such  a  regional  structure. 

Lassen  Peak  itself  was  the  center  of  fairly  extensive  glaciation,  which  reached 
its  maximum  after  the  period  of  major  volcanic  activity.  Some  of  the  later  lavas 
have  flowed  for  long  distances  down  valleys  cut  and  glaciated  into  lavas  of  earlier 
age.  Solfataric  action  has  continued  down  to  the  present  time,  however,  and 
in  a  consideration  of  the  eruptions  since  1914,  which  seem  to  be  exceptional  volcanic 
manifestations  in  many  ways,4  it  is  well  to  bear  in  mind  that  Lassen  Peak  itself 
has  been  relieved  of  its  ice  load  in  recent  times.  It  is  by  no  means  impossible  that 
some  isostatic  adjustment,  consequent  upon  the  relief  of  ice  load,  may  have  assisted 
the  mechanism  of  the  more  recent  outbursts. 

1  U.  S.  Geol.  Surv.  Geol.  Atlas,  Lassen  Peak  Folio,  1895. 

2  J.  S.  Oilier,  Klamath  Mountain  section,  California,  Am.  Journ.  Sci.  (4),  15,  342-362,  1903. 

3  J.  S.  Diller,  Hornblende  basalt  in  Northern  California,  Am.  Geol.,  19,  253-255,  1897. 

4  A.  L.  Day,  Possible  causes  of  the  volcanic  activity  at  Lassen  Peak,  Bull.  Seismol.  Soc.  Am.,  12,  35-46,  1922;  Journ. 
Franklin  Inst.,  194,  569-582,  1922.  J.  S.  Diller,  I.assen  I’eak — our  most  active  volcano,  Bull.  Seismol.  Soc.  Am.,  6,  1-7, 
1916. 


CHAPTER  1. 

SEQUENCE  OF  EVENTS. 

BEGINNING  OF  EXPLOSIVE  ACTIVITY. 

On  June  i,  1914,  the  following  telegram  was  sent  by  the  local  observer  of  the 
Forest  Service  at  Mineral,  California,  to  the  central  station  in  Sacramento. 

Mineral,  California,  June  1,  1914- 

State  Forester,  Sacramento,  California. 

Volcanic  eruption  of  Mount  Lassen  occurred  5  p.  m.  May  30th.  Crater  25  X  40  ft. 
with  lateral  fissures  formed.  Mud,  boulders,  and  sand  1  to  2  feet  deep  thrown  over  an 
area  200  feet  in  diameter.  Ranger  Abbey  examined  eruption  yesterday.  Heavy  volumes 
of  steam  rising  this  morning.  Crater  tj  mile  from  summit.  No  damage  yet. 

(Signed)  W.  J.  Rushing. 

This  brief  message  contains  the  first  trustworthy  record  of  the  outbreak  of  an 
active  volcano  within  the  boundaries  of  the  United  States  in  the  memory  of  men 
now  living. 

Lassen  Peak  (fig.  1),  or  Mount  Lassen,  as  it  is  frequently  called,  lies  in  north¬ 
eastern  California  near  the  southern  boundary  of  Shasta  County,  something  over 
200  miles  northeast  of  San  Francisco  and  about  75  miles  south  by  east  from  Mount 
Shasta.  It  forms  the  southern  extremity  of  the  Cascade  Range,  although  from 
neighboring  cities  (Redding,  Red  Bluff),  where  views  of  Lassen  Peak  are  obtained, 
it  appears  isolated  and  stands  out  quite  conspicuously  as  the  highest  point  in  a 
small  mountain  group  forming  a  portion  of  an  older  and  much  greater  center  of 
volcanic  activity  of  which  little  now  remains.  Its  height  as  given  by  the  U.  S. 
Coast  and  Geodetic  Survey  (1913)  is  10,466  feet  above  the  sea,  but  it  is  no  more 
than  4,500  feet  above  the  surrounding  teriane.  Its  nearest  neighbor,  Brokeoff 
Mountain,  is  a  part  of  the  rim  of  the  ancient  crater  of  Lassen  Peak,  but  its  activity 
has  long  since  ceased.  Only  a  few  feeble  sulphur  springs  remain  to  indicate  where 
the  northern  border  of  the  active  basin  may  have  been. 

Diller1  calls  attention  to  the  fact  that  Lassen  Peak  is  included  within  the  great 
outpouring  of  basalt  to  the  north,  which  forms  one  of  the  greatest  lava  fields  in  the 
world,  including  northern  California,  Oregon,  Washington,  Idaho,  and  a  part  of 
Wyoming,  covering  altogether  some  250,000  square  miles.  Nevertheless,  most  of 
the  exposed  lava  sheet  immediately  about  Lassen  Peak  is  andesite  rather  than 
basalt  and  suggests  that  we  are  here  in  a  transition  zone,  just  outside  rather  than 
within  the  great  “plateau”  basalt  field.  The  present  cone  is  made  up  of  a  rather 
dense  dacite,  not  unlike  the  dacite  of  Mont  Pelee  (Martinique),  and  presumably 


1  J.  S.  Diller,  Volcanic  History  of  Lassen  Peak,  Science,  N.  S.  43,  727,  1916. 


4 


of  high  viscosity  at  the  time  of  its  eruption.  The  lava  accordingly  piled  up  about 
the  opening  and  is  insignificant  in  volume  as  compared  with  the  great  basalt  out¬ 
pourings  to  the  northward,  which  were  for  the  most  part  relatively  fluid.1 

It  has  been  supposed  that  the  last  preceding  period  of  activity  of  the  present 
volcano  brought  to  the  surface  the  rough  region  known  as  Lassen  Crags,  just  north 
of  the  peak,  and  that  this  eruption  occurred  at  least  200  years  ago.2  Probably  the 
most  recent  volcanic  activity  in  the  region  occurred  some  10  miles  to  the  northeast, 
where  a  low  cone  (Cinder  Cone)  emerges  somewhat  abruptly  from  the  plain  and 


Fig  1. — June  9,  1914.  One  of  the  earliest  eruptions  of  Lassen  Peak.  Photo  Loomis. 


reaches  a  height  of  about  620  feet,  with  an  open  summit  crater  rather  more  than 
200  feet  deep.  From  the  side  of  this  cone,  at  an  elevation  not  much  above  the  level 
of  the  surrounding  plain,  there  emerged  a  flow  of  rough  lava  of  aa  type,  covering 
more  than  3  square  miles  and  from  100  feet  to  125  feet  in  thickness. 

From  Indian  tradition  the  age  of  this  flow  has  been  assumed  to  be  between 
75  and  100  years,  but  an  investigation  of  the  age  of  adjacent  trees3  indicates  that  a 
somewhat  greater  period  has  elapsed  since  this  flow  occurred.  So  far  as  we  have 

1  Cf.  H.  S.  Washington,  Deccan  Traps  and  other  plateau  basalts,  Bull.  Geol.  Soc.  America,  33,  775-780,  1922. 

2  Diller,  loc.  cit. 

3  At  the  suggestion  of  the  writer,  Supervisor  Merrill  of  the  Forest  Service  cut  down  one  of  the  trees  growing  about  3  feet 
from  the  flow  and  rooted  in  the  ash.  He  counted  more  than  200  rings  on  the  stump.  See  also  J.  S.  Diller,  A  Late  Volcanic 
Eruption  in  Northern  California  and  its  Peculiar  Lava.  U.  S.  Geol.  Surv.  Bull.  79,  20,  1891. 


record,  therefore,  the  only  local  volcanic  activity  during  the  past  century,  and 
perhaps  the  last  two,  has  taken  the  form  of  steam  fumaroles  and  hot  springs  in  the 
ancient  basin  to  the  southwest  of  Lassen  Peak  (Supan’s  Springs)  and  in  the  valleys 
to  the  south  and  southeast  of  it  (Morgan’s  Springs,  Bumpass  Hell,  Devil’s  Kitchen, 
The  Geyser,  Boiling  Lake,  etc.). 


Fig.  2. — 1891.  Inside  old  crater  looking  southeast.  Note  deposit  of 
snow  in  foreground.  Photo  Drew. 


Fig.  3. — The  bottom  of  the  old  crater  with  its  pool  of  water  draining  west¬ 
ward  through  the  western  notch  (left).  Photo  Yori. 


The  outbreak  of  May  30,  1914,  referred  to  in  the  Forest  Service  telegram 
quoted  above,  came  without  premonitory  symptoms  of  any  kind  having  been 
observed.  No  change  was  noticed  either  in  the  temperature  or  in  the  activity  ot 


6 


the  neighboring  hot  springs,  and  no  local  earthquakes  attracted  especial  attention. 
A  lowering  of  the  ground  water  so  often  observed  at  Vesuvius1  as  a  conspicuous 
premonitory  indication  of  impending  eruptions  was  not  noticed  here. 

The  valleys  surrounding  Lassen  Peak  for  a  distance  of  20  miles  or  more  are 
occupied  for  the  most  part  only  in  summer  by  cattlemen  and  lumbermen.  The 
nearest  point  of  observation  during  the  winter  season  is  probably  the  hamlet  of 
Mineral,  from  which  the  telegram  was  sent  and  which  is  regularly  used  as  a  winter 
observation  point  by  the  Forest  Service.  The  summer  observation  point  at  the 
summit  of  Lassen  Peak  itself  was  not  regularly  occupied  before  the  forest-fire 
season  (July). 


Fig.  4. — The  western  notch  in  the  crater  rim  before  the  upheaval  in  May,  1915.  Photo  Olsen. 

In  the  summer  season  Lassen  crater  was  reasonably  well  known  and  was 
accessible  to  and  occasionally  visited  by  tourists  before  any  sign  of  activity  appeared. 
In  appearance  the  crater  was  a  smooth  bowl  with  a  floor  of  volcanic  sand  and  lapilli, 
the  lowest  point  of  which  was  about  360  feet  below  the  highest  point  of  the  rim 
upon  which  the  Forest  Service  had  built  its  shelter.  A  small  pool  of  drainage  water 
was  usually  to  be  found  in  the  bottom  of  the  bowl  and  the  portion  of  the  inclosing 
parapet  which  faced  north,  was  never  free  from  snow  (figs.  2  and  3).  The  shape  of 
the  bowl  itself  was  roughly  oval,  with  the  long  axis  nearly  east  and  west,  but  it  was 
not  entirely  symmetrical.  The  north  and  south  sections  of  the  inclosing  rim 
retained  approximately  the  original  conical  form  but  the  east  and  west  sections  were 
broken  by  V-shaped  openings  (fig.  4),  pointing  to  earlier  explosive  action  and  per¬ 
haps  indicative  of  structural  weakness  in  this  azimuth.  It  is  interesting  to  note  in 
this  connection  that  the  general  faulting  of  the  region  (see  Diller)  is  in  a  nearly 


'•Joseph  Prestwich,  On  the  Agency  of  Water  in  Volcanic  Eruptions,  Proc.  Roy.  Soc.  No.  246,  1 1 7,  1886. 


7 


east-and-west  direction,  and  the  earliest  cracks  reported  from  the  present  eruption 
were  in  this  azimuth.  No  fumaroles  or  other  signs  of  latent  activity  are  known  to 
have  existed  on  the  summit  within  the  memory  of  those  living  near.  Snow  is 
reported  to  accumulate  within  the  summit  basin  to  a  depth  of  40  feet  or  more  each 


Fig.  5. — June  28,  1914.  Explosion  crater  showing  the  “lateral  fissures.” 

Photo  Holway. 


Fig.  6. — The  first  explosion  crater  showing  the  snow  with  ash  and  debris 
lying  upon  it.  Photo  Yori. 


winter,  and  it  may  or  may  not  be  noteworthy  that  the  time  of  the  initial  eruption 
corresponded  approximately  with  the  period  of  rapid  spring  melting  of  this  accu¬ 
mulated  snow,  and  that  streams  of  water  from  this  melting  snow  were  reported  to  be 


8 


pouring  into  the  new  crater  opening  in  the  very  earliest  announcements  of  the 
renewal  of  activity  (see  below). 

Notwithstanding  the  sparsely  inhabited  character  of  the  region,  the  first 
explosion  appears  to  have  been  plainly  seen  (from  Chester,  21  miles  away).  On  the 
next  day  Mr.  Harvey  Abbey,  of  the  Forest  Ranger  Service,  made  his  way  to  the 
summit  over  snow  and  found  an  opening  about  25  by  40  feet,  obviously  a  small 
explosion  vent  on  the  inside  of  the  crater  bowl,  between  the  small  pool  at  the  bottom 
of  the  bowl  and  the  northwestern  rim,  rather  less  than  half  way  up. 

The  early  photographs  of  the  explosion  crater  show  plainly  in  section  the  snow¬ 
bank  through  which  the  explosion  occurred  (figs.  5  and  6)  and  the  accumulated 
debris  of  the  explosion  scattered  over  the  top  of  the  snow.  It  is  obvious  from  these 
photographs  that  the  lapilli  and  fragmentary  ejecta  thrown  out  by  the  explosion 
were  cold,  otherwise  they  must  have  melted  their  way  into  the  snow  upon  which 
they  rested.  Steam  and  hot  water  within  the  explosion  crater  are  reported  by 
Ranger  Abbey,  but  tbe  solid  material  ejected  was  not  hot. 

Following  the  telegram  above  reported,  the  records  of  the  Forest  Service  con¬ 
tain  the  following  memorandum  under  date  of  June  2,  which  contains  some  further 
details : 

At  4  a.m.,  May  31,  Ranger  Abbey  left  Mineral  for  the  mountain,  arriving  on  top  at 
9  a.m.,  traveling  14  miles  over  snow  from  1  to  6  ft.  deep.  He  found  a  new  crater  25  X  40 
ft.  in  extent  and  about  300  ft.  from  the  top  on  the  north  side  of  the  small  lake.  There 
were  2  lateral  fissures  about  100  ft.  long  extending  from  the  crater.  Hot  mud,  stones  18 
inches  in  diameter,  and  sand  had  been  thrown  over  an  area  200  ft.  in  diameter  to  a  depth 
of  one  to  two  feet  [See  fig.  6].  Ashes  and  fine  sand  were  scattered  over  an  area  of  about 
one  mile  across.  A  large  quantity  of  hot  water  had  run  down  the  slope  into  the  lake, 
cutting  a  channel  in  the  snow.  Large  volumes  of  steam  were  being  blown  out,  and  there 
was  a  continual  loud  hissing.  Large  quantities  of  water  from  the  snow  were  pouring  into 
the  crater,  also  sand,  gravel,  and  boulders  from  the  sides.  Abbey  approached  to  within 
50  ft.  of  the  brink,  but  owing  to  the  caving  bank  it  was  unsafe  to  approach  closer.  The 
entire  disturbance  acts  more  like  a  geyser  than  a  volcano. 

(Signed)  W.  J.  Rushing. 

The  following  extract  is  taken  from  a  letter  addressed  by  the  local  supervisor 
to  the  district  forester  at  San  Francisco  under  date  of  June  9,  1914. 

Such  wild  stories  are  being  circulated  concerning  Mount  Lassen  that  I  am  sending  you 
the  results  of  our  observations  to  date. 

Saturday,  May  30,  an  outbreak  occurred  at  5  p.m.  This  was  witnessed  by  Ike  McKen¬ 
zie  of  Chester,  who  was  looking  directly  at  it  when  it  occurred.  Abbey  investigated  it 
Sunday,  May  31  ...  .  (see  telegram  above).  .  .  .  The  sand  thrown  out  was  granitic  in 
character,  sharp,  and  contained  mica.  No  molten  material  was  thrown  out  at  all.  At 
8h5m  a.m.,  June  1,  a  second  outburst  occurred,  throwing  out  large  quantities  of  the  same 
material.  Some  boulders  weighing  all  of  a  ton  were  thrown  out.  The  vent  was  enlarged 
to  60  X  275  ft.  I  he  fumes  escaping  were  said  by  Boerker  and  Macomber  to  be  arsenic  [?J, 
hydrochloric  acid,  and  sulphur.  Boerker,  Abbey,  and  Macomber  went  up  June  4,  re¬ 
mained  at  the  top  in  the  lookout  house  over  night,  and  came  back  June  5.  .  .  . 

We  have  watched  it  carefully  and  at  no  time  have  we  been  able  to  see  any  flame  or  in¬ 
dication  of  fire.  .  .  . 


(Signed) 


W.  J.  Rushing. 


PLATE  1 


Successive  views  of  the  explosion  of  June  14,  1914,  taken  near  Manzanita  Lake.  Photo  Loomis. 


9 


For  the  next  few  days  eruptions  continued  at  the  rate  of  about  one  every  two 
days  and  were  of  increasing  violence  and  duration.  The  fourth  recorded  outbreak, 
which  occurred  at  4h30m  p.m.  on  June  8,  continued  for  40  minutes  and  was  heavier 
than  any  which  preceded  it.  On  Friday,  June  12,  the  ash  cloud  was  very  dense 
and  poured  out  for  50  minutes  or  more.  It  was  after  this  eruption  that  a  visit  to 
the  summit  showed  that  the  explosion  crater  had  increased  to  400  feet  in  length 
and  ico  feet  across,  the  inner  walls  and  bottom  being  formed  of  infallen  talus. 

Sunday,  June  14,  brought  three  eruptions,  during  one  of  which  the  ash  cloud 
reached  an  elevation  of  2,500  feet  above  the  summit,  and  explosions  of  great  power 
were  reported.  After  the  eruption  of  Friday,  June  19,  the  explosion  crater  had  grown 
to  600  feet  in  length  and  100  feet  across  (fig.  7),  evidently  extending  eastward  along 


Fig.  7. — June  20,  1914.  Looking  north.  Explosion  vent  now  600  ft.  long  and  100  ft.  wide. 

Photo  Loomis. 


a  preexisting  summit  fault.  During  this  period  of  development  a  considerable 
number  of  people  visited  the  mountain  and  made  photographs  and  observations  of 
various  kinds.  One  party  was  so  unfortunate  as  to  be  caught  in  the  midst  of  a 
severe  outbreak  (June  14,  9h43m  a.m.),  during  which  a  member  of  the  party  suffered 
a  broken  shoulder  from  a  falling  stone,  and  all  were  obliged  to  bury  their  heads  in 
the  snow  to  avoid  breathing  the  dust-laden  air.  The  darkness  within  the  cloud  was 
reported  to  be  intense  for  a  period  of  10  minutes  or  more,  but  suffocating  gases 
were  not  encountered.  (Plate  I.) 

In  general  during  the  summer  of  1914  the  eruptions  continued  to  increase  in 
violence.  On  July  15,  for  example,  a  very  heavy  eruption  at  6h5m  a.m.  was  reported 
which  lasted  4  hours  and  was  followed  at  I2h5ra  on  the  same  day  by  the  greatest 
disturbance  thus  far  recorded.  It  lasted  during  the  entire  afternoon  and  vast 
quantities  of  dust  were  discharged.  This  period  of  activity  (1914)  probably 


10 


culminated  in  the  outbreak  of  Saturday,  July  18,  beginning  at  5  h28m  in  the  morning. 
Of  this,  the  record  kept  by  the  Forest  Service  states.  “By  far  the  most  violent 
eruption  to  date.  Ash,  steam,  etc.,  arose  to  height  of  11,000  feet  practically  entire 
morning.”  This  eruption  is  No.  24  of  the  Forest  Service  record  (No.  30  of  the 
combined  record  hereto  appended,  p.  176). 

Following  this  outbreak  the  mountain  was  quiet  until  August  10,  when  a 
moderate  quantity  of  ash  was  thrown  out  in  the  late  afternoon  and  early  evening. 
Under  date  of  August  15,  Forest  Supervisor  Allen  reported  to  Mr.  Diller  of  the 
Geological  Survey  that  a  tape  measurement  of  the  explosion  crater  showed  it  to  be 
600  feet  by  209  feet.  Other  outbreaks  followed  during  the  summer,  notably  on 
August  21,  when  the  entire  crater  appeared  to  be  active  and  the  smoke  cloud 
reached  a  measured  elevation  of  10,560  feet  above  the  summit.  Following  is  an 
abstract  from  a  letter  from  Supervisor  Rushing  dated  August  27,  1914,  describing 
the  activity  of  this  period: 

The  eruptions  of  last  week  were  considerably  heavier  than  any  formerly  seen,  and  the 
eruption  of  August  19  was  plainly  heard  by  parties  entering  the  Manzanita  Chute  [distant 
about  5  miles  northwest  of  the  mountain].  From  the  west  end  seven  vibrations  were  felt 
by  Ranger  Bramhall  at  Jessen  and  Stuart’s  place  in  section  30,  T.  31  N.,  R.  5E.  [distant 
5  miles  northeast;  reference  is  to  Forest  Service  map  of  Lassen  National  Forest,  1913]. 
Rumblings  and  noises  similar  to  rocks  sliding  have  been  heard  by  the  lookout  on  Brokeoff 
Mountain  [4  miles  southwest]  during  all  recent  eruptions.  There  is  only  one  crater  so  far 
as  we  can  determine.  .  .  .  Rumors  of  new  craters  are  caused  by  parties  seeing  the  ashes 
or  dust  being  blown  by  whirlwinds  from  different  parts  of  the  Mountain  .  .  . 

From  this  time  on  eruptions  were  of  greater  duration  and  heavily  ash-laden, 
but  apparently  of  more  moderate  violence.  The  total  number  of  outbreaks  re¬ 
corded  at  the  Forest  Service  observation  stations  during  the  year  1914  is  69  (from 
all  sources  no).  Of  these,  the  first  17  (up  to  July  13)  were  sharp  and  short,  none 
lasting  more  than  an  hour.  The  eighteenth  eruption  (July  15)  lasted  4  hours,  and 
of  the  following  outbreaks  up  to  and  including  the  forty-ninth  (September  30, 
1914)  but  two  are  described  as  short,  the  average  length  being  3  to  4  hours.  From 
the  fiftieth  outbreak  (October  1)  to  the  end  of  the  year  but  one  eruption  (the 
fifty-third  October  7)  exceeded  an  hour  in  length,  (see  p.  176,  et  seq.). 

CHARACTER  OF  EXPLOSIONS  OF  1914. 

The  discussions  of  volcanic  activity  at  Lassen  Peak  by  newspapers  and  random 
observers  have  not  served  to  set  before  us  a  very  clear  picture  of  the  actual  activity 
there  as  compared  with  other  volcanic  eruptions  of  historic  record.  The  number  of 
observers  was  actually  small,  by  reason  of  the  isolated  location  of  the  volcano,  and 
the  proportion  of  these  who  had  seen  volcanic  phenomena  before  was  almost  negli¬ 
gible.  It  is,  therefore,  not  surprising  if  the  emphasis  has  occasionally  been  mis¬ 
placed  in  the  accounts  which  have  come  to  us  of  the  different  phases  of  activity.  * 
By  way  of  illustration,  it  will  be  recalled  that  a  rather  serious  discussion  took  place 
in  newspapers,  in  which  one  or  two  magazines  of  local  circulation  participated,  as 
to  whether  Lassen  Peak  should  properly  be  described  as  a  volcano  or  a  geyser,  the 


11 


latter  apparently  being  suggested  by  one  of  the  earliest  Forest  Service  dispatches 
(p.  8),  by  the  steam  clouds,  and  by  the  report  of  streams  of  hot  water  within  the 
crater  basin.  This  point  need  never  have  been  in  doubt.  Lassen  Peak,  both  in  the 
visible  record  of  past  activity  and  in  the  characteristics  of  the  present  eruption,  is 
a  true  volcano. 

The  precise  character  of  the  explosions  which  occurred  during  1914  can  not  be 
determined  from  information  available  on  the  ground.  No  report  of  fumes  of 
sulphur  or  acid  in  the  smoke  cloud  itself  has  come  from  any  observer.  During  1914 
acid  fumes  in  insignificant  volume  were  twice  reported  on  the  mountain,  once  by 
the  Forest  Service  and  once  by  Mr.  Diller  of  the  Geological  Survey,  but  neither  of 
these  reports  was  connected  with  the  more  violent  phases  of  activity.  Neither  have 


Fig.  8. — October  27,  1914.  The  explosion  crater  and  its  vertical  rift.  Photo  Olsen. 

any  reports  indicated  the  presence  of  incrustations  or  precipitated  matter  on  the 
rocks  exposed  by  the  explosions.  There  was  steam  at  all  times,  both  in  the  explosion 
clouds  and  pouring  from  cracks  and  loose  ejecta  (fig.  8),  both  during  and  after  the 
explosions.  Practically  all  reports  from  visitors  to  the  mountain,  as  well  as  photo¬ 
graphs  taken  at  the  summit,  confirm  this.  It  would  almost  seem  as  though  the 
explosions  of  the  first  summer  were  altogether  of  the  steam-boiler  type  without  the 
participation  of  fresh  lava  or  more  than  insignificant  quantities  of  the  more  active 
chemical  ingredients  common  to  the  explosive  volcanoes  of  the  West  Indies  or  the 
Mediterranean. 

The  absence  of  any  evidence  of  continued  high  temperature  on  the  mountain 
appears  to  confirm  this  conclusion,  for  all  of  the  phenomena  observed  during  the 
summer  of  1914  could  have  been  produced  by  exploding  steam  without  attaining 
high  temperatures  locally.  The  further  fact  that  most  of  the  outbreaks  were  of 


12 


low  intensity  and  large  volume  also  suggests  the  same  interpretation.  The  single 
recorded  observation  of  red-hot  objects  (Forest  Service,  see  below)  thrown  out  of 
the  crater  offers  little  to  disturb  this  view.  It  is  altogether  possible,  considering  the 
volume  of  dust  and  heavier  ejecta  removed  from  the  crater  by  the  successive  ex¬ 
plosions  continuing  through  several  months,  that  for  a  few  moments  red-hot  rocks 
should  have  become  exposed  and  a  few  fragments  ejected  while  still  hot  enough  to 
show  red,  but  the  evidence  in  support  of  such  a  hypothesis  is  meager. 

This  question,  whether  or  not  liquid  lava  appeared  in  the  crater  in  1914  or 
red-hot  rocks  were  thrown  out,  has  been  somewhat  difficult  to  answer  conclusively. 
The  newspapers  reported  such  occurrences  very  early,  and  isolated  observers  re¬ 
ported  having  seen  such  displays  at  night  during  the  summer  months.  It  is  hardly 
possible  to  give  full  credence  to  such  observations  so  long  as  they  remain  entirely 
isolated  and  lack  all  precision  of  detail.  With  the  mountain  under  constant  ob¬ 
servation  from  all  directions  in  a  time  like  this,  a  real  display  of  glowing  lava  or 
bombs  would  certainly  find  more  than  one  observer  when  it  occurred,  and  would 
leave  unmistakable  traces  after  its  conclusion.  The  reports  of  the  character  of  these 
displays  are  very  incomplete,  some  reporting  red-hot  rocks  and  others  brilliant  white 
flashes.  No  one  with  whom  the  writer  has  talked  has  ever  described  a  full  flight 
of  any  hot  object  (in  1914),  including  its  fall  and  landing,  although  the  mountainside 
was  in  plain  view  to  many  observers  (cf.  observations  of  1915,  pp.  18,19). 

A  glow  in  the  heavens  at  night  was  reported  on  one  or  two  occasions  from 
Chester,  but  this  observation  also  is  subject  to  a  certain  amount  of  reservation  in 
view  of  the  fact  that  the  sunset  during  the  summer  months  is  behind  the  mountain. 
From  Chester  illuminated  clouds  are  often  seen  in  the  west  in  the  evening  hours 
without  any  unusual  significance  being  attached  to  them.  Such  a  glow  was  not 
reported  from  other  places,  nor  was  it  reported  from  Chester  during  the  darkest 
hours  of  the  night  in  1914.  The  only  authentic  statement  of  reasonably  positive 
character  bearing  upon  this  subject  during  this  year  is  found  in  the  Forest  Service 
records. 

September  30,  1914. 

Mr.  R.  B.  Holway, 

Mr.  Wade,  the  lookout  on  Turner  Mountain  [15  miles  to  the  south],  distinctly  saw 
luminous  bodies  which  appeared  to  him  to  be  red-hot  stones  thrown  out.  He  counted 
17  distinct  luminous  bodies.  The  same  phenomenon  was  seen  by  several  parties  at  Chester. 
This  is  the  first  time  that  any  forest  officer  has  seen  indications  of  fire  or  molten  material 
although  on  at  least  two  other  occasions  private  parties  asserted  that  they  saw  what  ap¬ 
peared  to  them  to  be  fire.  The  crater  has  opened  up  on  the  west  side  of  the  mountain  for 
a  considerable  distance  and  considerable  quantities  of  steam  issue  from  its  entire  length. 

(Signed)  W.  J.  Rushing. 

No  other  incident  of  the  kind  appears  in  the  records  of  the  Forest  Service.  In 
reply  to  an  inquiry  from  the  Geological  Survey  upon  this  subject  the  following 
positive  statement  was  received: 

December  14,  1914. 

Mr.  J.  S.  Diller, 

We  have  no  record  of  anyone  having  visited  the  crater  lately,  so  can  not  quote  any 
proof  of  heat  except  as  given  by  our  Turner  Mountain  lookout  as  described  in  my  letter 


13 


of  November  7.  [Repeats  information  contained  in  letter  addressed  to  Professor  Holway 
on  September  30,  quoted  above.] 

The  eruption  upon  November  18  was  seen  by  me  from  near  Reading,  and  I  feel  posi¬ 
tive  that  there  is  a  vent  somewhere  near  the  base  of  the  mountain  on  the  north  side,  al¬ 
though  no  one  has  verified  this  by  finding  a  crater  there.  The  crater  on  the  west  side  near 
the  top  is  much  enlarged  and  the  entire  west  slope  of  the  mountain  is  discolored  by  volcanic 
dust. 

(Signed)  W.  J.  Rushing. 

In  endeavoring  to  reach  a  proper  conclusion  regarding  these  occurrences,  we 
should  not  overlook  the  fact  that  all  these  eyewitnesses  were  viewing  volcanic 
phenomena  for  the  first  time.  This  is  not  primarily  to  question  the  available 
evidence,  but  rather  to  emphasize  the  need  of  bringing  experience  to  bear  on  the 
interpretation  of  this  evidence,  for  which  purpose  the  introduction  of  trustworthy 
observations  elsewhere  may  be  profitably  invoked.  The  observeis  reported  bright 
objects  in  flight  above  the  crater.  It  is  a  natural  inference,  but  not  a  necessary 
consequence,  that  these  moving  objects  were  blocks  of  hot  lava.  Such  witnesses  as 
I  had  the  good  fortune  to  talk  with  afterward  were  uncertain  about  important 
details  which  were  necessary  to  establish  this  conclusion.  They  were  not  sure,  for 
example,  whether  the  flying  objects  were  red  or  white,  nor  did  they  observe  that 
they  fell  to  the  ground.  The  record  of  the  eyewitnesses  during  the  year  1914  is 
confined  to  the  observation  of  moving  objects  appearing  to  emerge  with  the  explo¬ 
sion  cloud  from  the  crater,  but  which  were  not  seen  to  leave  the  cloud  or  to  fall. 

In  explanation  of  this  may  be  placed  a  fact  of  common  observation  in  all  violent 
volcano  outbreaks,  that  dust-laden  clouds  shot  out  at  high  velocity  frequently 
develop  electrical  phenomena  due  to  the  friction  of  the  dust  particles  in  passing 
swiftly  through  the  air.  These  electrical  flashes  are  widely  variable  in  color  and 
behavior  with  the  intensity  of  the  explosion  and  the  dust  content,  and  at  distances 
of  20  miles  may  easily  have  suggested  more  tangible  objects. 

To  this  we  may  perhaps  add  that  during  the  year  1914  no  volcanic  ejecta  show¬ 
ing  evidence  of  recent  heat  were  found,  either  on  the  summit  or  flanks  of  the 
mountain,  despite  a  most  diligent  search.  It  is  particularly  noteworthy  in  this  con¬ 
nection  that  all  the  early  photographs  of  the  crater  show  the  ejecta  lying  on  the 
surface  of  the  snow,  without  sinking  through  it.  There  can  be  no  question  of  red-hot 
rocks  in  that  period.  Neither  were  any  fires  started  in  the  surrounding  forest  after 
the  snow  had  melted,  though  dry  leaves  are  kindled  by  contact  at  temperatures 
far  below  red  heat.  Such  scanty  evidence  offers  no  very  tangible  ground  for  sup¬ 
posing  that  any  of  the  explosions  of  1914,  violent  and  long-continued  as  they  were 
during  the  summer  months,  reached  down  to  a  zone  of  red  heat. 

A  still  more  positive  and  convincing  proof  of  this  is  available  which  has  not 
been  cited  hitherto.  Charley  Yori,  who  frequently  served  as  a  local  guide  in  the 
Lassen  Peak  region,  is  thoroughly  familiar  with  the  seasonal  appearance  of  the 
mountain,  both  before  and  during  its  period  of  activity.  His  report  that  the 
accumulation  of  snow  on  the  summit  was  uncommonly  heavy  during  the  following 
winter  (1914-15)  is  therefore  entitled  to  full  confidence  and  has  been  confirmed  by 
other  visitors.  This  observation  bears  directly  upon  the  question  of  high  crater 


14 


temperatures  during  1914.  If  red-hot  lava  had  been  exposed  on  the  summit  during 
the  summer  and  autumn  of  that  year,  heavy  snow  accumulations  upon  it  during  the 
following  winter  would  have  been  impossible.  Indeed,  in  the  winter  of  1915-16, 
when  moderately  hot  material  did  fill  the  crater,  no  snow  accumulated  within  the 
area  of  activity. 

During  the  winter  opportunities  for  observation  are  rare  and  usually  poor. 
The  summit  is  surrounded  by  clouds  and  covered  with  snow.  Except  for  explosions 
of  sufficient  power  to  penetrate  above  local  clouds  and  so  be  observed  at  considerable 
distances,  the  reports  of  the  winter  of  1914-15  must  be  regarded  as  incomplete. 
There  were  no  visitors  to  the  summit  before  March,  and  there  is  no  record  of  changes 
in  the  observed  conditions  there. 

Although  the  explosions  continued  to  occur  at  intervals  of  a  few  days  through 
the  autumn  and  winter  of  1914,  scattering  ash  and  small  fragments  for  miles  to  the 
eastward  under  the  prevailing  wind,  the  intensity  of  the  explosions  gradually 
diminished.  In  making  comparisons  of  this  kind,  however,  it  should  be  borne  in 
mind  that  there  is  no  proper  measure  of  the  intensity  of  such  explosions.  The 
Forest  Service,  in  default  of  other  standards,  based  its  estimates  on  the  height  of  the 
dust  cloud  above  the  summit,  but  this  is  hardly  a  measure  even  of  the  volume  of  the 
blast,  for  the  puffs  vary,  not  only  in  intensity  but  in  direction  and  in  duration,  and, 
furthermore,  several  new  openings  are  believed  to  have  participated  in  the  winter 
activity.  Within  a  period  of  4  or  5  months  during  the  winter  season,  probably  no 
activity  was  observed  from  a  point  nearer  than  the  Poorest  Service  Station  near 
Mineral,  15  miles  to  the  southward.  The  number  of  outbreaks,  however,  was 
carefully  recorded,  in  so  far  as  they  were  visible  in  daylight. 

CULMINATION  OF  EXPLOSIVE  ACTIVITY,  MAY  19-22,  1915. 

In  May  the  accumulated  snows  of  winter  begin  to  melt  at  this  elevation.  All 
observers  agree  that  the  quantity  of  snow  on  the  mountain  in  the  winter  1914-15 
was  uncommonly  large.1  The  drifts  in  the  bays,  high  up  on  the  flanks  of  the 
mountain  to  the  south  and  northeast,  immediately  adjacent  to  the  peak,  were 
probably  not  less  than  50  feet  deep.  The  crater  conditions  characteristic  of  the 
first  stage  of  activity  (first  year)  were  last  observed  by  E.  N.  Hampton  on  March  23, 
1915,  when  an  ascent  to  the  summit  was  made  and  several  photographs  of  the 
explosion  crater  were  taken.  From  these  photographs  it  appears  that  the  new 
explosion  crater  had  grown  almost  to  the  full  size  of  the  old  crater  bowl.  It  is 
described  as  nearly  circular  and  about  1,000  feet  in  diameter. 

Between  this  visit  and  the  more  violent  activity  of  May  following,  certain  other 
physical  changes  at  the  summit  were  indicated  to  observers  at  a  distance,  though  just 
what  these  changes  were  and  howthey  occurred,  whether  by  continuous  slow  upheaval 
or  as  the  result  of  successive  explosions,  it  is  impossible  to  say.  Mr.  B.  F.  Loomis, 

1  Records  at  nearby  stations  of  the  U.  S.  Weather  Bureau  are  as  follows:  Snowfall  at  Chester  (elevation  4,550  feet)  191 1- 
12,  91.5  in.;  1912-13,  155.2  in.;  1913-14,  210.1  in.;  1914-15,  183.2  in.  Snowfall  at  Inskip  (elevation  4,975  feet)  1911-12, 
151.6  in.;  1 9 1 2—  1 3 ,  232.6  in.;  1913-14,  233.7  in.;  1914-15,  250.4  in.  Climatological  Data  for  United  States,  Northeastern 
California,  pp.  31,  33,  U.  S.  Weather  Bureau,  1916. 


15 


observing  from  Anderson,  which  lies  to  the  west  of  the  mountain,  about  45 
miles  distant,  was  the  first  to  detect  a  small  black  mass  pushing  up  into  the  cleft 
in  the  rim  on  the  western  summit.  Miss  Alice  Dines,  postmistress  at  Manton  (20 
miles  west),  in  a  private  letter  June  8,  1916,  writes  of  similar  changes:  .  .  “the 

dark  formation  began  to  rise  above  the  level  of  the  mountain  about  the  16th  or 


Fig.  9. — May  22,  1915.  The  great  eruption  seen 
from  the  east.  Photo  Yori. 


1 8th  of  May,  black  during  a  clear  day.”  This  change  appears  not  to  have  been 
noticed  elsewhere  and  no  observer  hazarded  the  winter  ascent  in  pursuit  of  further 
information.  It  would  appear  from  these  two  bits  of  evidence,  made  by  two  inde¬ 
pendent  and  most  faithful  observers  of  occurrences  at  Lassen  Peak  throughout  the 
eruptive  period,  that  the  crater  had  been  partially  filled  from  below  before  the  great 
eruption  of  May  19  took  place.1 


1  See  also  Appendix  under  May  19  !'D”,  p.  1S2. 


16 


First  Appearance  of  Glowing  Lava. 

On  May  19  an  eruption  occurred  which  for  volume  and  intensity  probably 
overshadowed  anything  which  had  preceded,  but  which  was  but  imperfectly  ob¬ 
served  because  it  occurred  during  the  night.  Mr.  Olsen,  from  the  leeward  side  of 
the  mountain  (Chester),  says:  “Lassen  seen  this  afternoon  the  first  time  for  six 
days.  Was  in  eruption  all  the  time  it  was  visible.  After  dark  a  steady  glow  of  light 
was  seen  shining  on  cloud  of  smoke  for  several  hours.” 

Miss  Dines,  from  her  viewpoint  on  the  opposite  (windward)  side  ol  the  moun¬ 
tain,  enjoyed  a  more  favorable  view.  She  says  “Mountain  smoked  all  day.  Fire 
lava  seen  on  top  at  9  p.m.” 

The  first  report  from  the  Forest  Service  came  in  a  telegram  at  ioh30m  p.m. 
from  ranger  Seaborn  at  Jessen  and  Stewart’s  place  to  the  northward  of  the  moun¬ 
tain:  “First  indication  of  eruption  was  tremendous  flood  of  mud,  etc.,  down  Flat 
Creek.  Meadows  covered.” 

G.  R.  Milford  telegraphed  on  May  20  to  Mr.  Diller  ol  the  Geological  Survey, 
Washington,  as  follows:  “Lassen  Peak  in  violent  eruption  9h30m  to  ioh30m  last 
night.  Fire  observed  coming  from  crater.  Incandescent  ejecta  roll  down  the 
mountainside.  I  observed  the  spectacle  from  Volta,  10  miles1  from  Lassen  Peak. 
Many  in  Sacramento  Valley  saw  the  same.” 

This  graphic  telegram  was  later  supplemented  by  a  letter  (November  17,  1916) 
to  Mr.  Diller,  which  we  are  permitted  to  quote  practically  entire: 

Ever  since  May  of  1914,  when  Lassen  Peak  first  showed  indications  of  springing  into 
life,  and  taking  its  place  among  the  more  or  less  active  volcanoes  of  the  world,  reports  have 
been  circulated  from  time  to  time  as  to  the  observance  of  fire  within  and  coming  from  the 
crater.  These  reports  when  thoroughly  investigated,  lacked  substantiation  and  corrobora¬ 
tion,  both  as  to  the  hour  the  fire  was  visible  and  also  as  to  its  duration  and  magnitude. 
However,  it  was  not  until  the  night  of  May  19,  1915,  that  the  observance  of  an  eruption 
accompanied  by  fire  of  sufficient  magnitude  and  duration  was  so  generally  noted  and  cor¬ 
roborated.  On  that  date  the  writer  was  at  the  Volta  plant  of  the  Northern  California  Power 
Company  Cons.,  this  plant  being  located  about  21  miles  due  west  of  Lassen  Peak. 

About  9hi5m  p.m.  word  was  sent  in  by  telephone  that  Lassen  Peak  was  in  eruption 
and  fire  could  be  seen  coming  from  the  crater.  In  company  with  Mr.  and  Mrs.  Chas.  R. 
Milford,  Miss  Catherin  Milford,  Mr.  C.  E.  Johnson,  Mr.  and  Mrs.  F.  A.  Dooley,  Mr.  and 
Mrs.  Geo.  Risley,  the  writer  went  to  a  point  of  vantage  about  100  yards  southeast  of  the 
power  house,  where  an  unobstructed  view  of  the  peak  could  be  had,  and  there  found  that 
reports  were  true  and  that  the  mountain  was  in  eruption  and  fire  could  be  observed  coming 
from  the  crater. 

Our  attention  was  first  drawn  to  the  deep-red  glow  which  appeared  over  the  crater  and 
was  of  sufficient  intensity  to  illumine  the  entire  outline  of  the  mountain  top.  There  was  no 
moon,  the  heavens  were  clear,  yet  this  glow  was  bright  enough  to  be  reflected  in  the  dense 
clouds  of  steam  and  smoke  arising  from  the  crater.  From  time  to  time  the  glow  seemed 
to  change  in  brilliancy,  now  brighter,  now  dimmer — this  variation  due,  no  doubt,  to  the 
varying  density  of  the  clouds  of  steam  and  smoke  issuing  from  the  crater. 

As  we  continued  to  gaze  at  the  wonderful  spectacle,  the  glow  commenced  to  increase 
in  brilliancy,  now  brighter,  now  still  brighter,  until,  behold,  the  whole  rim  of  the  crater 
facing  us  was  marked  by  a  bright-red  fiery  line  which  wavered  for  an  instant  and  then, 


1  Obviously  an  error;  Volta  is  21  miles  west  of  Lassen  Peak.  See  Milford’s  letter  following;. 


17 


in  a  deep-red  sheet,  broke  over  the  lowest  part  of  the  lip  and  was  lost  to  sight  for  a  moment, 
only  to  reappear  again  in  the  form  of  countless  red  globules  of  fire  about  500  feet  below  the 
crater’s  lip.  These  globules,  or  balls  of  fire,  were  of  varying  size,  the  largest  appeared  at 
that  distance  (21  miles)  about  3  feet  in  diameter,  the  smallest  appeared  as  tiny  red  sparks. 
All  maintained  their  brilliancy  as  they  rolled  down  the  mountainside  until  lost  to  sight  be¬ 
hind  the  intervening  range  of  hills. 

These  phenomena  took  place  at  intervals  of  about  8  minutes  for  a  period  of  some  2 
hours,  and  to  the  writer  it  appeared  as  though  he  were  looking  at  a  titanic  slag-pot  being 
slowly  filled  by  molten  slag  in  some  smelter.  The  glow  over  the  rim  gradually  increased 
in  intensity  until  the  pot’s  rim  was  brilliantly  marked  by  the  appearance  of  slag  itself. 
Finally,  the  slag  spills  over  the  lip  in  a  vivid  red  sheet  and,  as  it  runs  down  upon  and  into 
the  slag  dump,  it  breaks  through  the  crust  of  older  slag  and  appears  against  the  back¬ 
ground  as  splashes  of  deep-red  molten  material. 

As  stated  earliest  in  this  article  we  watched  this  re-occurring  boiling-over,  as  it  were, 
of  the  crater  for  a  period  of  two  hours,  at  the  end  of  which  the  activity  seemed  to  decrease. 
Concluding  that  the  display  for  that  evening  was  nearly  at  an  end,  we  returned  to  the 
power  house  and  made  preparations  for  a  trip  on  the  morrow  to  Manzamta  Lake,  which 
lies  almost  at  the  foot  of  the  mountain. 

Next  day  proved  a  disappointment,  as  the  sky  was  overcast  and  the  peak  was  shrouded 
in  dense  storm  clouds.  Nevertheless  we  started,  and  arrived  at  the  lake  about  10  in  the 
morning.  At  brief  intervals  the  clouds  would  break  sufficiently  to  permit  us  to  see  the 
peak,  which  was  steaming  and  smoking  in  great  volumes,  indicating  that  the  activity  had 
immensely  increased.  We  also  observed  that  there  was  on  the  western  slope  a  dark  mass 
of  matter  appearing  almost  black.  This  mass  appeared  about  1,000  feet  across  and  ex¬ 
tended  down  the  slope  for  possibly  a  distance  of  2,000  or  2,500  feet.  From  our  location 
this  mass  appeared  like  volcanic  mud  and  must  have  been  of  a  consistency  greater  than 
ordinary  mud,  as  the  surface  still  maintained  its  roughed,  furrowed  appearance. 

Of  direct  observation  of  this  eruption  there  is  little  more  than  is  contained  in 
this  account,  the  mountain  was  shrouded  in  cloud  and  darkness,  except  from  the 
west  (windward)  side,  where  the  glow  of  incandescent  matter  was  seen  by  the  Mil¬ 
ford  party  and  by  Miss  Dines.  Mr.  Milford’s  record,  considering  the  distance 
away,  is  clear  and  positive.  Sufficient  incandescent  matter  was  visible  at  the 
summit  to  illuminate  the  summit  outline  and  the  smoke  column  above  it  at  a  dis¬ 
tance  of  21  miles,  and  some  appearance  of  movement  there  was  plainly  visible. 
The  incandescent  mass  which  he  describes  to  resemble  a  slag-pot  overflowing  at 
intervals  of  8  or  10  minutes  does  not,  upon  close  examination  afterward,  appear  to 
have  been  a  flow.  There  is  no  evidence  of  recent  fluidity  in  the  ejected  material; 
it  appears  rather  to  be  a  shattered  portion  of  the  solid  volcanic  plug  uplifted  through 
the  western  cleft  in  the  crater  rim  along  with  the  general  upheaval  of  the  crater 
bottom.  The  bright  spots  which  Milford  describes  as  splashes  of  “deep-red” 
molten  material  were  probably  due  to  the  breaking  off  of  hot  fragments  revealing 
fresh  red-hot  surfaces  which  flashed  out  and  then  gradually  cooled,  while  the  separ¬ 
ated  fragment  rolled  down  the  mountainside.  The  lava  is  andesite  of  such  extreme 
viscosity  that  no  splash  is  possible  at  the  deep-red  temperature  described.  Neither 
does  the  form  of  the  ejected  material  show  any  evidence  of  recent  fluidity.  Sharp 
edges  are  not  rounded  nor  side  walls  sagged.  The  total  surface  of  the  triangular 
mass  which  Mr.  Milford  saw  was  about  1,000  feet  long  from  the  crater  rim  to  the 
terminating  point  (fig.  10)  and  about  300  feet  wide  at  the  rim. 


18 


It  also  appears  from  Milford’s  letter  that  he  does  not  believe  the  rumors  ot 
glow  on  the  mountain  and  red-hot  fragments  thrown  out  before  this  date,  that 
is,  during  the  year  1914,  to  be  true.  Supervisor  Merrill,  of  the  Forest  Service,  who 
was  stationed  within  view  of  the  mountain  throughout  this  period,  told  me  that  he 
was  of  the  same  opinion.  There  were  violent  and  long-continued  explosions  dis¬ 
charging  great  quantities  of  ash  which  no  doubt  caused  occasional  electrical  dis¬ 
plays,  but  there  is  no  tangible  evidence  of  the  appearance  of  incandescent  matter 
in  the  crater  until  the  night  of  May  19,  1915,  nearly  a  year  after  the  beginning  of 
the  outbreak. 


Professor  Rulifif  S.  Holway,  of  the  University  of  California,  appears  to  have 
been  the  first  to  visit  the  summit  crater  after  (5  days  after)  this  upheaval.  Not 
only  this  fact,  but  his  comment  gains  especial  interest  and  weight  from  the  fact 
that  he  is  one  of  the  very  few  experienced  geologists  who  have  studied  this  erup¬ 
tion  on  the  ground.  He  says: 

There  were  also  many  reports  that  the  volcano  had  ejected  red-hot  boulders  and  molten 
lava.  The  writer  examined  the  rocks  in  several  of  the  localities  credited  with  having 
received  such  deposits,  but  so  far  has  found  none  differing  from  the  characteristic  rocks 
of  the  old  crater.  Nor  were  there  found  any  rocks,  old  or  fresh,  bearing  evidence  of  recent 
fusion.  It  seems  very  probable  that  molten  lava  has  been  near  the  surface,  and  it  is  quite 
possible  that  small  quantities  have  been  ejected.  There  are  many  reports  from  trustworthy 
people  that  “flames”  have  been  seen.  The  writer,  with  a  good  field  glass,  watched  until 
after  dark  the  diminishing  puffs  of  steam  and  dust  of  the  eruption  of  June  16.  Shortly 
after  sunset  he  saw  apparently  most  perfect  flames  shoot  up  from  the  crater’s  rim. 


PLATE  2 


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19 


However,  as  the  sun  sank  lower  those  apparent  flames  became  entirely  dark,  except  for  the 
highest  part  of  the  column.  A  minute  or  two  later  the  entire  jet  became  wholly  dark. 
There  remain,  however,  reports  of  luminous  objects  and  glows1  seen  3  or  more  hours  after 
sunset,  for  which  the  writer  can  not  account. 

FIRST  HORIZONTAL  BLAST  AND  MUD  FLOW,  MAY  19,  1915. 

Some  important  features  of  this  eruption,  which  Mr.  Milford  describes  so 
graphically,  were  concealed  by  darkness  and  remained  unsuspected  until  some 
time  afterward.  No  one  knew,  for  example,  that  there  was  also  a  horizontal  blast 
which  swept  down  the  opposite  (east)  side  of  the  mountain  with  sufficient  power 
to  carry  everything  before  it.  Not  only  were  the  snow  and  the  forest  trees  swept 
away,  but  even  the  surface  of  the  ground  was  swept  clean.  The  primary  results  of 
this  blast  escaped  observation  for  the  moment,  but  the  great  avalanche  of  mud  and 
water,  boulders,  and  forest  debris  which  resulted  from  it  poured  down  the  moun¬ 
tainside  along  the  valley  of  Lost  Creek,  in  part  over  the  divide  into  Hat  Creek,  and 
thence  around  a  sharp  bend  to  the  northward  in  an  overwhelming  flood  which  was 
reported  by  Ranger  Seaborn  (p.  16),  7  or  8  miles  below.  These  parallel  valleys, 
Hat  Creek  and  Lost  Creek,  contained  fertile  meadows  which  were  usually  occupied 
by  herdsmen  later  in  the  season.  On  the  morning  oi  May  20  these  meadows  were 
found  covered  to  the  depth  of  5  or  6  feet  with  debris  of  this  destructive  flood,  which 
the  newspapers  forthwith  described  as  a  flow  from  the  crater  itself.  This  erroneous 
conclusion  was  corrected  by  Professor  Holway  a  week  later,  and  by  Loomis,  who 
visited  it  2  days  after  its  occurrence.  His  resume  in  the  Anderson  Valley  News  of 
March  17,  1922,  is  as  follows: 

It  was  on  May  20,  1915,  that  the  first  great  eruption  of  Lassen  Peak  occurred.  An 
immense  amount  of  hot  water,  steam,  and  hot  rocks  were  thrown  out  on  the  east  side. 
There  were  deep  snowdrifts  on  the  east  side,  and  this  mass  of  hot  stuff  melted  the  snow 
and  the  whole  mass  ran  down  the  mountainside,  taking  everything  before  it.  There  was 
a  heavy  growth  of  timber  there  before  the  flood,  hut  this  was  all  swept  away.  A  great 
part  of  this  mud  and  water  ran  down  Lost  Creek,  while  the  other  part  crossed  over  the 
divide  and  went  into  Hat  Creek. 

Four  ranches  were  washed  away  by  the  flood.  Nelson  Stewart’s  place  on  Hat  Creek, 
Adams’s  place  on  Lost  Creek,  and  Lost  Camp,  and  yet  farther  down  the  Perkiss  place. 
The  flood  not  only  washed  the  land  away,  but  left  the  places  covered  with  logs  and  rocks 
everywhere.  The  Perkiss  place  was  formerly  a  flat  meadow,  but  now  there  are  a  hundred 
rocks  or  more  from  5  to  10  feet  in  diameter  where  formerly  there  were  no  rocks  at  all. 
[Plate  2.] 

1  For  example:  “Nelson  Olsen  of  Chester,  who  kept  a  notebook  of  happenings  on  the  mountain,  said  he  had  moved  his 
bed  so  as  to  see  the  mountain  constantly  from  his  window  at  night,  but  had  only  once  (2h30m  a.m.,  May  15,  1915)  seen 
evidence  of  hre.  He  described  the  phenomenon  as  a  series  of  flashes  coming  from  the  crater  and  shooting  upward  like  Roman- 
candle  balls.  Several  in  number.  Short  flights.  Lasted  5  minutes.  In  reply  to  a  question  whether  they  appeared  white  or 
red,  he  said  white,  and  added  that  he  thought  at  the  time  that  they  might  be  electric  flashes,  as  they  expired  high  in  the  air 
without  returning  to  the  ground.”  (Day,  Field  notes  of  May  13,  1916.) 

“Charley  Yori,  the  Lassen  Peak  guide,  also  of  Chester,  said  he  had  heard  from  Olsen  of  the  above  observation  and  later, 
in  'the  month  of  October,  1915,  had  seen  flashes  himself.  Asked  what  they  looked  like,  he  said  ‘Lightning’.”  (Day,  Field 
notes  of  May  13,  1916.) 

“  Miss  Kelly,  schoolmistress  at  Chester,  said  that  she,  in  company  with  the  driver  of  the  Chester-Red  Bluff  stage  (who  was 
present  and  confirmed  the  observation)  had  seen  unmistakable  bright-red  flashes  on  the  night  of  October  29  or  30,  which  went 
out  suddenly  and  were  not  seen  to  descend.  I  suggested  that  red-hot  rocks  would  have  to  be  very  large  to  be  seen  at  a  distance 
of  25  miles  and  that  if  very  large,  could  hardly  ‘  go  out  suddenly’.  She  thought  they  might  be  electrical  flashes.”  (Day,  Field 
Notes  of  June  x,  1915.) 


20 


Wid  Hall  lived  at  Old  Station  on  Hat  Creek,  20  miles  from  Lassen.  .  .  .  Halls’ 
folks  .  .  .  left  the  door  open  on  leaving  and  the  mud  filled  the  house  up  to  the  window¬ 
sills.  This  loaded  the  house  down  and  kept  it  from  floating  away. 

Professor  R.  S.  Holway,  writing  in  the  Sunset  Magazine  for  August  1915, 
describes  the  occurrences  in  a  similar  way  after  a  study  of  the  situation  on  the 
ground.  He  says: 

In  this  gorge  the  winds  drift  the  winter’s  snows,  making  a  huge  snow  field  which  lasts 
through  the  summer.  During  the  period  in  which  Lassen  has  been  erupting  ashes  the  wind 
has  drifted  them  also  into  this  same  gorge,  making  the  conditions  ideal  for  a  flood  of  mud 
and  water. 

Naturallv  this  hot  volcanic  dust  has  melted  the  snow  and  caused  mud  flows.  The 
writer  has  followed  actually  flowing  mud  on  the  side  of  the  cone  to  the  edge  of  the  crater 
and  found  at  the  head  of  the  flow  dry  dust  wherever  the  rim  was  bare  rock,  and  moistened 
dust  where  it  rested  on  snow,  thus  disproving  the  current  reports  that  mud  flows  really 
issued  from  within  the  crater  itself.  On  the  crater  nm  no  mud  seemed  to  have  been 
ejected  from  the  crater.  The  most  reasonable  theory  for  the  big  flood  down  the  two  creeks, 
the  swiftness  and  power  of  which  can  scarcely  be  exaggerated,  seems  to  be  the  following, 
viz.,  that  on  the  accumulated  mass  of  snow  and  volcanic  dust  in  Lost  Creek  gorge  there  fell 
a  mass  of  steam  and  dust  from  the  eruption  of  May  20,  a  mixture  which  probably  came  in  a 
blast  directed  downward  by  a  sudden  explosion. 

Origin  of  the  Mud  Flow. 

A  second  difficulty  in  establishing  the  mud  flow  as  a  direct  outflow  from  the 
crater  occurs  when  the  attempt  is  made  to  follow  the  mud  stream  to  its  source. 
Instead  of  fixing  by  this  means  a  connection  between  the  mud  flow  and  the  crater, 
all  trace  of  the  mud  flow  is  lost  on  the  mountainside  1,500  feet  or  more  below  the 
crater  rim  (fig.  n).  Although  no  eyewitness  of  its  actual  formation  and  progress 
has  been  found,  a  most  careful  search  fails  to  reveal  any  tangible  connection  on  the 
surface  ot  the  ground  between  the  mud  flow,  now  hard-baked  and  standing  in  its 
tracks,  as  it  were,  and  the  explosion  crater.  It  has  proved  quite  impossible  to  find 
support  for  the  view  that  the  crater  sent  forth  this  or  any  other  mud  flow,  as  such, 
during  the  eruption  of  May  19.  W.  H.  Spaulding,  who  visited  the  summit  on 
May  30,  says:  “The  first  reports  were  that  the  mountain  had  belched  mud  which 
had  flooded  Hat  Creek  Valley  to  the  north  and  Lost  Creek  and  Manzanita  Lake 
to  the  south  and  west  of  the  mountain.  Our  examinations  showed  no  mud  flow 
out  of  the  mountain.”  Neither  has  the  more  or  less  obvious  suggestion  that  the 
mud  may  have  issued  through  a  secondary  opening  near  the  foot  of  the  mountain 
found  any  supporting  evidence  on  the  ground. 

To  an  observer  of  this  scene  4  weeks  after  the  explosion  occurred,  when  prac¬ 
tically  nothing  was  changed  and  yet  the  storm  had  cleared  away,  so  that  all  parts 
of  the  field  were  accessible,  the  true  course  of  events  appeared  obvious,  even  with¬ 
out  the  evidence  of  an  eyewitness.  Lost  Creek  has  its  source  in  a  mass  of  snow  and 
ice  (fig.  11,  left)  which  fills  a  great  shallow  bay  on  the  outer  (eastern)  flank,  reach¬ 
ing  nearly  to  the  summit  of  the  mountain.  Within  this  bay  the  snow  accumulates 
to  such  depth  in  the  winter  season  that  all  of  the  summer  heat  is  normally  inade¬ 
quate  to  melt  it  away.  (Compare  snow  deposit  of  1916,  Plate  5.)  This  year  in 


21 


particular  we  know  that  the  volume  of  snow  was  very  great,  and  even  at  the  time 
ot  these  observations  (July  i)  a  small  body  of  ice  remained  on  the  upper  slope,  sud- 
plying  the  head-waters  ol  Lost  Creek.  The  great  mass  of  snow  which  had  filled 
this  basin  in  May  had,  therefore,  disappeared  completely  in  one  night,  and  in  place 
of  it  we  had  the  flood  or  mud  flow.  There  is  no  other  outlet  for  such  a  quantity 
of  water  on  the  one  hand,  and  no  evidence  of  any  other  source  of  the  water  neces¬ 
sary  to  the  flow  except  the  melted  snow  and  the  hot,  ash-laden  rain  condensing 
from  the  steam  explosions.  Condensed  volcanic  steam,  falling  as  hot  rain  charged 


Fig.  I  1. — July  14,  1915.  The  northeast  flank  of  the  mountain  where  the  horizontal  blasts 
and  the  flood  originated.  Upper  left,  snow  left  after  passing  of  horizontal 
blast.  Upper  center  (dark),  eastern  end  of  the  upheaved  lid,  fumaroles  indicat¬ 
ing  continuation  of  fault.  Lower  right,  beginning  of  mud  flow.  Photo  Day. 

with  ash,  bathed  the  summit  and  melted  the  adjacent  snow,  forming  rivers  of 
mud,  not  only  in  the  valleys  of  Hat  Creek  and  Lost  Creek  but  upon  the  west,  north¬ 
west,  and  north  slopes  also.  One  of  these,  accumulating  in  the  Manzanita  Lake 
drainage  basin  (northwest),  covered  many  acres  and  reached  the  proportions  of 
a  considerable  flood,  though  it  caused  no  serious  damage  to  the  large  forest  trees 
in  its  track  and  so  remained  practically  unnoticed. 

It  was,  however,  not  the  mud  flow  but  a  volcanic  blast  of  terrific  power  (nuee 
ardente)  and  moderately  high  temperature,  heavily  charged  with  dust  and  rock 
fragments,  delivered  at  a  low  angle  in  an  east-northeast  direction  down  Lost 
Creek  Valley,  which  cleared  the  valley  of  its  immense  trees  and  indeed  of  every 
moveable  object  for  more  than  4  miles.  When  accompanied  by  ash  and  con- 


22 


densed  steam  from  the  cloud  and  directed  upon  the  accumulated  snow  a  torrent  of 
fresh  mud  was  an  inevitable  but  secondary  consequence. 

There  appears  to  be  no  need  to  base  this  deduction  upon  grounds  of  probabil¬ 
ity,  for  many  direct  observations  of  the  effects  of  the  horizontal  blast  are  available. 
Before  May  19  the  valley  of  Lost  Creek  is  reported  by  the  Forest  Service  to  have 
contained  5,000,000  feet  of  standing  timber  (original  forest),  much  of  which  reached 
the  diameter  of  3  to  5  feet.  After  that  date  the  bottom  of  the  valley  was  swept 


12  13 


14  13 

Timber  and  boulders  swept  down  Lost  Creek  by  the  mud  flow  of  May  19,  1915. 


Fig.  12. — June  4,  1915.  Logs  piled  on  the  divide  between  Lost  Creek  and  Hat  Creek. 

Photo  Seaborn. 

Fig.  13. — July  18,  1915.  Boulders  and  tree  trunks,  Lost  Creek  Valley.  Photo  Day. 

Fig.  14. — June  4,  1915.  Boulder  from  Lassen  Peak  carried  for  4  miles  by  the  mud  flow  of 
May  19,  1915.  Photo  Seaborn. 

Fig.  15. — June  4,  1915.  Log  jam  below  Jessen  Meadow.  Photo  Seaborn. 

like  a  floor,  and  was  left  without  stumps  or  roots  to  indicate  its  previous  forest 
cover.  It  was  hard  to  find  even  a  pebble  in  that  area  greater  than  a  few  inches 
in  diameter.  In  the  lower  reaches  of  the  valley  this  floor  still  carries  its  covering 
of  baked  mud  flow,  sometimes  2  or  3,  sometimes  5  or  6  feet  deep,  and  it  is  only  when 
one  arrives  at  the  far  end  of  the  devastated  region  that  the  disposition  of  the  boul¬ 
ders  from  the  summit  and  the  timber  which  once  covered  the  valley  begins  to  be 
evident.  Here  are  giant  trees  broken  and  twisted  into  fantastic  groups,  with 
here  and  there  a  boulder  weighing  up  to  15  tons  or  more  (figs.  12,  13,  14,  15).  As 
stated  above,  this  cleaning-out  of  the  timber  cover  of  the  valley  was  not  accom- 


23 


plished  in  the  first  instance  by  the  mud  flow,  because  the  valley  walls  are  clean 
far  above  any  point  reached  by  the  mud.  It  requires  hardly  more  than  a  glance, 
however,  to  show  what  the  agent  must  have  been,  for  higher  up  on  the  inclosing 
sides  of  the  valley,  a  little  at  the  side  of  the  main  axis  of  the  blast,  we  find  the  forest 
trees  down  but  not  removed,  and  in  particular  we  find  them  lying  in  parallel  rows 
for  nearly  2  miles,  with  their  tops  pointing  uniformly  away  from  the  crater.  It 
is  quite  possible  to-day  to  ride  a  horse  through  these  avenues  of  parallel  trunks 
lying  prostrate  in  faultless  alignment,  upon  which  a  force  must  have  been  expended 
which  did  not  distinguish  between  saplings  of  a  few  inches  and  the  oldest  giants 
of  the  forest. 


Fig.  16. — July  14,  1915.  View  across  Lost  Creek  Valley  S  to  N  showing  the  timber  lying 
away  from  the  blast  and  across  the  hillside.  In  the  foreground  the  center 
of  the  path  of  the  blast  now  swept  clean.  Photo  Day. 


One  must  not  fail  to  note  also  that  these  parallel  rows  of  trunks,  as  they  line 
the  inclosing  walls  of  the  valley,  are  not  in  the  position  of  rest  to  which  a  tree  trunk 
falling  on  a  steep  hillside  would  normally  attain,  namely,  pointing  down  the  slope. 
On  the  contrary,  without  exception,  they  lie  along  the  contour  lines  in  the  position 
least  stable  of  all  (fig.  16).  Even  the  force  of  gravity  aiding  the  fall  of  the  trees  was 
quite  powerless  to  dictate  their  position  in  competition  with  the  force  of  the  blast 
which  laid  them  low. 

Another  interesting  observation  may  be  made  in  this  outer  zone  at  the  side  of 
the  blast.  Most  of  the  trees  which  line  these  corridors  were  uprooted,  but  some 
were  broken  off  a  few  feet  above  the  ground  instead.  The  standing  stumps  of  such 


24 


bear  unmistakable,  direct  evidence  of  the  bombardment  which  they  received. 
Without  exception,  their  bark  is  gone  on  the  side  toward  the  mountain,  while  fully 
retained  on  the  protected  side.  Similarly,  the  exposed  wood  on  the  side  toward  the 
mountain  is  completely  peppered  with  fine  sand,  oftentimes  driven  in  for  a 
considerable  fraction  of  an  inch.  Indeed,  as  one  nears  the  source  of  the  outburst 
the  intensity  of  this  bombardment  was  that  of  a  fierce  sand-blast  which  rounded  off 
the  stumps  themselves  (fig.  17).  The  power  of  this  blast  was  sufficient  to  carry 
away  all  the  trees  and  the  vegetation  in  Lost  Creek  Valley  and  those  covering 
the  divide  between  Lost  Creek  and  Hat  Creek  to  the  eastward.  It  also  con- 


Fig.  17. — June  28,  1915.  The  path  of  the  blast  showing  the  sand-blasted  trunks  on  the 
south  border.  Photo  Day. 


tinued  on  across  the  Jason  Meadows  and  laid  low  most  of  the  trees  for  perhaps 
half  a  mile  on  the  far  side  of  the  divide.  The  total  length  of  the  devastated  area  in  a 
straight  line  from  the  point  of  outbreak  on  the  mountain  eastward  to  its  greatest 
extent  is  more  than  4  miles.  The  area  is  in  general  fan-shaped  (fig.  29)  following 
the  contour  of  Lost  Creek  Valley  and  widening  out  below  to  an  extreme  width  of 
perhaps  a  mile  and  a  quarter.  On  the  boundaries  adjacent  to  this  area  the  trees 
are  down,  but  were  not  carried  away,  and  all  the  transition  stages,  down  to  com¬ 
paratively  insignificant  damage,  may  be  observed.  Branches  broken  by  falling  rocks 
are  found  in  all  directions  for  2  miles  or  more  about  the  devastated  area. 


PLATE  3 


May  22,  1915.  Lassen  Peak  and  Lost  Creek  Valley  after  the  first  and  before  the  second  horizontal  blast.  Photo  Loomis. 
Note  the  group  of  standing  trees  (right)  which  are  down  in  subsequent  views  (Plate  4). 


25 


SECOND  HORIZONTAL  BLAST,  MAY  22,  1915. 

There  is  trustworthy  evidence  that  not  all  of  the  damage  observed  in  the 
valleys  ol  Hat  Creek  and  Lost  Creek  was  done  by  a  single  blast.  There  appear  to 
have  been  two  ot  these,  the  one  just  described,  occurring  on  the  night  of  May  19, 
and  one  accompanying  the  culminating  eruption  on  the  afternoon  of  May  22.  The 
evidence  ol  this  is  contained  in  a  photograph  of  the  mountain  from  Hat  Creek 
Valley  made  by  B.  F.  Loomis  in  the  early  afternoon  of  May  22,  just  before  the 
greatest  eruption  occurred.  In  this  photograph  the  effects  of  the  first  explosion 
and  ol  the  resulting  flood  are  plainly  shown,  but  a  group  of  forest  trees  on  the  north 
side  of  Lost  Creek  Valley  (on  the  right,  Plate  3)  is  still  standing  in  this  picture,  while 


Fig.  18. — May  24,  1915.  Minor  mud  flows  on  the  north  and  west  flanks  of  the  mountain 
due  to  falling  ash  and  condensed  steam  melting  the  snow.  Photo  Loomis. 


in  subsequent  views  they  are  down  (Plate  4).  No  other  essential  change  has 
been  noted  between  this  and  the  later  views.  There  was  a  second  flood  accom¬ 
panying  the  eruption  of  May  22,  but  the  snow  had  been  carried  out  by  the  earlier 
blast,  so  that  the  water  causing  the  second  flood  must  have  been  furnished  almost 
entirely  by  the  condensing  steam  from  the  explosions  themselves.  Further  evidence 
of  this  is  found  in  the  fact  that  three  other  mud  flows  of  secondary  magnitude 
accompanied  the  eruption,  on  the  west,  northwest,  and  north  sides  of  the  mountain 
respectively,  as  shown  in  another  photograph  by  Loomis,  taken  on  May  24  (fig.  18). 


26 


Of  these  minor  mud  streams  of  May  22,  which  were  witnessed  by  Loomis,  he  says 
(private  letter  April  20,  1922): 

I  have  a  photograph  taken  in  the  morning  of  May  22  which  shows  white  snow  to  the 
summit  and  only  one  black  streak  on  the  west  side,  where  a  small  mud  flow  probably  went 
down  in  the  eruption  of  May  19.  In  fact,  the  snow  was  white  to  the  summit  when  the  great 
eruption  of  May  22  began,  and  directly  afterward  we  saw  the  streams  start  down  the  sides 
of  the  Peak  .  .  .  These  mud  streams  did  not  start  before  the  great  eruption,  nor  after¬ 
ward,  but  while  the  great  eruption  was  on  .  .  .  It  is  unthinkable  that  water,  either  cold 
or  hot,  would  flow  over  the  crater  rim  in  gentle  ripples,  while  hot  rocks  and  mud  bombs 
were  being  hurled  into  the  air  a  mile.  But  I  know  that  hot  water  fell  in  the  form  of  rain 
which  started  the  mud  flow,  because  nothing  else  could  have  done  it. 

Of  the  second  great  blast  and  accompanying  mud  flow  down  the  east  slope  of 
the  mountain  following  Lost  Creek  Valley,  Loomis  says  ( Anderson  Valley  News , 
Anderson,  California,  March  17,  1922): 

On  this  second  big  eruption  (May  22)  a  second  flood  went  down  Lost  Creek,  but  not  so 
large  as  the  first  one.  Very  little  snow  was  left  to  be  melted,  so  that  the  water  from  the 
crater  (ram)  was  the  greater  part  of  the  column  of  water  that  went  down.  Another  fright¬ 
ful  thing  happened  there  to  add  to  the  damage  caused  by  the  flood.  Hot  steam  flew  out 
through  that  slit  in  the  east  side  of  Lassen,  which  blew  down  across  the  heads  of  Lost  and 
Hat  Creeks  and  blew  down  every  tree  for  a  space  of  a  mile  wide,  and  on  the  outer  edge  of 
this  area  the  trees  were  burned  to  a  crisp  with  the  hot  steam. 

PERIOD  OF  SUBSIDENCE. 

Following  the  great  eruption  of  May  22,  the  volcano  entered  upon  a  period  of 
gradual  subsidence,  interrupted  at  intervals  by  sporadic  activity,  but  none  of  a 
magnitude  comparable  with  the  great  eruption  or  even  of  the  heavier  eruptions  of 
the  previous  year. 

During  June  eight  eruptions  were  recorded,  all  of  short  duration;  during  July, 
six,  the  last  of  which  was  fairly  heavy  and  accompanied  by  rumblings  which  were 
heard  several  miles  away.  In  September  and  October  nineteen  were  recorded,  two  of 
which  are  reported  to  have  been  accompanied  by  bright  flashes  as  though  bombs 
were  being  shot  high  in  the  air,  but  which  were  probably  electrical  effects  (page 
19).  During  November  and  December  there  was  but  one  eruption  of  consequence 
(November  13),  and  in  the  winter  following  no  signs  of  activity  were  noted. 

In  view  ol  the  fact  that  the  first  outbreak  occurred  late  in  the  month  of  May, 
during  the  period  of  most  rapid  melting  of  the  accumulated  snow  of  winter,  and  the 
maximum  intensity  of  action  was  reached  in  the  same  month  of  the  following  year 
(1915)  under  like  conditions,  it  was  deemed  of  importance  to  make  a  trip  to  the 
mountain  in  May  ol  1916  in  order  to  ascertain  whether  the  snow  conditions  ot  this 
season  could  be  definitely  associated  with  the  intensity  of  volcanic  activity.  Ac¬ 
cordingly,  the  month  of  May  and  part  of  June  following  was  spent  on  or  near  the 
mountain. 

It  may  be  said  at  once  that  so  far  as  this  primary  purpose  is  concerned,  nothing- 
conclusive  could  be  ascertained,  for  the  reason  that  the  major  portion  ol  the  exposed 
plug  on  the  summit  remained  warm  enough  to  prevent  any  accumulation  of  snow 


PLATE  4 


July  22,  1915.  Lassen  Peak  from  the  northeast  showing  the  devastated  area  after  the  blast  of  May  22,  1915.  Photo  Day 
Note  the  absence  of  the  trees  on  the  right  which  are  standing  in  Plate  3. 


M  f  iBH&fiY 

or  let 

UMro.snr*  n 


27 


on  it  during  the  winter  of  1915-16.  At  the  time  of  our  visit  on  May  22,  the  anni¬ 
versary  of  the  great  eruption,  there  was  no  snow  to  be  seen  in  the  crater,  except  on 
the  surrounding  rim,  and  in  consequence  there  was  no  surface  water  to  be  disposed  of. 
Whether  it  is  a  consequence  of  this  or  not,  there  was  also  no  activity  observable  during 
the  period  of  our  visit,  save  only  a  few  fumaroles,  notably  on  the  northeast  slope 
below  the  lid  at  the  point  of  origin  of  the  two  great  horizontal  blasts  of  1915. 


Fig.  1 9. — July  26,  1915.  The  bottom  of  the  summit  crater  after  the  great  eruption  of  May  22,  1915. 

Photo  Loomis. 

Fig.  20. — July  15,  1915.  Rift  extending  radially  down  the  north  flank  of  Lassen  Peak  after  the 
great  eruption  of  May  22.  Photo  Day. 

During  the  remainder  of  the  year  (1916)  only  two  eruptions  of  noteworthy 
magnitude  appear  to  have  been  noticed  (October  16  and  24).  The  year  1917  began 
with  a  serious  show  of  activity  on  January  17,  and  in  the  month  of  May  some 
powerful  eruptions  of  several  hours’  duration  were  noted.  The  smoke  cloud  rose  to 
a  height  of  12,000  feet  on  May  18  during  an  eruption  of  6  hours’  duration,  and  on 
May  19  and  20  activity  was  nearly  continuous.  It  is  of  considerable  interest  to  note 
that  this  brief  resumption  of  sustained  activity  not  only  falls  at  the  same  period  of 


28 


the  year  as  the  initial  outbreak  in  1914  and  the  period  of  maximum  activity  in 
1915,  but  also  that  considerable  quantities  of  snow,  accumulated  during  the 
previous  winter,  were  again  available  (Plate  5).  Eruptions  followed  this  resumption 
of  violent  activity  almost  daily  until  the  middle  of  June,  when  the  extinction 
became  practically  complete.  Smoke  clouds  were  reported  sporadically  thereafter 
by  the  newspapers  and  by  various  observers,  but  it  is  not  likely  that  any  of  these 
represented  true  eruptions.  Indeed,  many  of  them  were  nothing  more  than 
movements  of  dust  under  the  action  of  the  wind. 

During  this  period  of  activity  of  May  and  June  (1917),  however,  some  explo¬ 
sions  occurred  of  such  violence  as  to  displace  large  masses  of  material  at  the  top  of 
the  mountain,  and  materially  to  change  the  appearance  of  the  crater.  So  far  as 
known,  this  is  also  the  only  period  following  the  great  eruption  ot  1915  when  such 
displacements  occurred. 


Fig.  21. — July  7,  1922.  Summit  of  Lassen  Peak.  Shal¬ 
low  1917  crater.  Photo  Day. 


At  the  close  of  the  activity  of  1915  there  were  two  major  centers  of  eruption- 
one  within  the  old  crater  at  the  northeast  corner  of  the  crater  bowl  (fig.  19),  de¬ 
veloped  by  the  activity  of  1914  and  1915,  the  other  outside  the  cone  on  the  north, 
where  a  radial  crack  (fig.  20)  several  hundred  feet  in  length  opened  some  time  dur¬ 
ing  the  period  of  maximum  activity  (May  19-22,  1915),  from  which  most  of  the 
subsequent  eruptions  took  their  origin.  In  1915  this  crack  was  no  more  than  a  few 
feet  wide,  but  during  the  activity  of  1917  it  increased  in  magnitude  to  a  crater  about 
500  feet  in  diameter  and  possibly  300  feet  deep,  separated  now  by  only  a  thin  wall, 
probably  less  than  50  feet  thick  at  any  point,  from  the  older  inside  crater  above 
referred  to.  Indeed  at  the  top  40  to  50  feet  of  this  wall  has  been  blown  away  so 
that  the  two  craters  are  now  nearly  merged. 

There  is  also  a  third  center  of  activity  which  developed  in  1917  within  the 
periphery  of  the  old  crater  rim,  immediately  to  the  west  of  the  inside  crater  above 
referred  to,  and  possibly  200  feet  distant  from  it.  This  crater  is  both  larger  and 
shallower  than  the  others,  but  around  the  margin  of  it  are  to  be  found  the  only 
fumaroles  which  persist  at  the  top  of  the  mountain.  These  are  not  seriously  active 


PLATE  5 


m  utt h*«r 

Or  THfc 


29 


and  the  highest  temperature  noted  among  them  during  our  visit  of  this  year  (July 
1922)  was  790.  This  third  crater  is  probably  not  more  than  75  feet  in  depth  below 
the  general  level  of  the  upheaved  plug,  and  lies  immediately  to  the  east  of  that 
portion  of  the  western  rim  which  is  still  standing  (fig.  21).  Through  the  courtesy 


Fig.  22. — Lassen  Peak  from  the  air  (northwest)  showing  all  three  summit 
craters. 

Beginning  at  the  arrow  left: 

(1)  The  outside  rift  (Fig  20)  after  its  enlargement  in  1917.  This  crater 

was  the  center  of  most  of  the  activity  subsequent  to  the 
great  eruption  of  May  1915. 

(2)  The  main  crater  in  1914  and  1915  (Fig.  19).  Origin  of  the  catastro¬ 

phic  eruptions  of  May  19  and  22,  1915. 

(3)  A  shallow  summit  crater  (Fig.  2 1 )  developed  in  1917.  Photograph  by 

U.  S.  Army  Air  Service.  From  National  Geographic  Maga¬ 
zine,  Copyright  1 924. 


of  the  Army  Air  Service  and  the  National  Geographic  Society  it  is  possible  to  show 
the  relation  of  the  three  summit  craters  of  Lassen  Peak  which  have  survived  from 
the  eruptions  of  1917.  The  photograph  (fig.  22)  is  taken  from  the  air  above  and 
to  the  northwest  of  the  summit. 


30 


So  far  as  may  be  ascertained  from  the  present  appearance  of  the  summit,  this 
entire  period  of  activity  is  now  closed.  There  are  no  signs  to  indicate  its  early 
return. 

SUMMARY  OF  FIELD  OBSERVATIONS. 


Gathering  together  for  purposes  of  discussion  the  various  threads  of  evidence 
that  have  been  followed  thus  far  in  their  chronological  sequence,  we  may  divide  the 
present  activity  into  three  periods:  (i)  the  activity  of  1914  and  the  early  months 
of  1915,  during  which  the  culmination  was  approaching;  (2)  the  devastating  erup¬ 
tions  of  May  19  and  22,  1915,  including  the  upheaval  of  the  crater  floor  which  was 
the  only  lava  movement  recorded;  (3)  the  slow  subsidence  from  May  1915  through 
the  year  1917. 


23  24 

Figs.  23,  24. — June,  1914.  Explosions  encountered  on  the  summit  by  Robertson’s 
party.  Photo  Robertson. 


Considering  these  periods  in  this  order,  the  first  comprehends  the  long  series 
of  explosive  eruptions  that  occurred  at  intervals  of  2  or  3  days  for  almost  a  full 
year,  the  intensity  increasing  rapidly  from  the  beginning  in  May  to  the  late  autumn 
and  then  diminishing  during  the  winter  season  preceding  the  violent  outbreak  of 
the  following  May  (1915).  At  the  time  of  the  first  outbreak  the  crater  bowl  was 
filled  with  snow  to  a  depth  varying  from  15  to  40  feet,  and  the  rapid  melting  under 
the  hot  May  sun  was  at  its  height.  The  initial  eruption  was  explosive  in  character, 
sending  up  a  cloud  of  “smoke”  to  a  height  of  several  hundred  feet  and  scattering 
small  fragments  and  miscellaneous  debris  from  the  bottom  of  the  old  crater  to  a 
distance  of  200  feet  or  more  in  all  directions.  The  succeeding  explosions  were 
characterized  by  violent  outbursts  of  steam,  some  white  and  some  black  with  their 


31 


load  of  ash  (figs.  23,  24),  ascending  to  different  heights  from  a  few  hundred  to 
11,000  feet  above  the  summit  and  continuing  from  1  to  4  hours.  Stones  from  a 
few  inches  to  2  feet  in  diameter  were  scattered  in  all  directions,  reaching  an  extreme 
distance  of  4  miles  on  the  leeward  (east)  side  of  the  mountain.  The  fine  ash  floated 
eastward  under  the  prevailing  wind  for  a  much  greater  distance.  The  ejected  rock 
fragments  were  cold  and  remained  on  the  top  of  the  snow  without  melting  their  way 
in.  During  this  period  the  dust  exerted  no  melting  action  upon  the  snow  which  it 
covered.  After  the  first  eruption  the  forest  rangers  noticed  two  cracks  extending 
in  general  direction  east  and  west  from  the  explosive  opening,  and  out  of  these 
cracks  clouds  of  steam  were  exhaled.  The  snow  adjacent  to  the  cracks  and  to  ihe 
explosion  opening  was  melting  and  considerable  quantities  of  water  flowed  into 
the  cracks  and  so  into  the  bottom  of  the  explosion  crater,  where  it  disappeared  in 
the  talus  without  forming  a  pool. 

Other  eruptions,  following  the  first  at  intervals  varying  from  a  few  hours  to  2 
or  3  days,  showed  increasing  intensity  and  duration,  the  explosion  crater  becoming 
rapidly  enlarged  as  the  explosions  succeeded  one  another.  The  general  direction 
of  growth  of  the  explosion  crater  was  east  and  west,  apparently  following  the  initial 
cracks,  which  also  correspond  in  general  direction  to  the  rift  in  the  cone  and  to  the 
faulting  in  the  Lassen  Peak  region,  since  studied  by  Diller. 

The  period  from  July  13  to  October  1  included  all  of  the  more  powerful  explo¬ 
sions  of  1914,  and  the  average  duration  of  the  activity  was  3  to  4  hours.  From 
October  1  to  May  of  the  following  year  explosions  were  less  frequent  and  of  only 
moderate  violence.  It  is  altogether  likely  that  many  of  the  explosions  of  this 
period  escaped  observation  by  reason  of  the  short  days  and  the  winter  clouds  and 
snow. 

Little  information  gathered  in  this  period  of  activity  appears  to  bear  very 
directly  upon  its  possible  cause.  That  the  explosions  were  steam  explosions,  in 
which  neither  chemical  reactions  nor  extreme  temperatures  played  any  visible  part, 
appears  to  be  established.  Evidence  of  heat  on  the  summit  and  in  the  ejecta  is  almost 
entirely  wanting.  The  explosions  were  for  the  most  part  of  comparatively  large  vol¬ 
ume  and  low  intensity  when  compared  with  typical  eruptions  of  Vesuvius,  for 
example.  This  conclusion  is  equally  true,  whether  it  be  based  on  the  height  of  the 
explosion  cloud  or  on  the  size  and  character  of  the  ejecta.  The  explosion  cloud  was 
heavily  dust-laden  always,  but  it  rarely  rose  to  great  heights,  nor  was  it,  in  this 
period,  ever  observed  to  be  hot  or  strongly  acid  either  by  persons  coming  in  contact 
with  it  or  from  its  effects  on  vegetation. 

Similarly,  the  ejecta  thrown  out  during  this  year  were  composed  entirely  of 
small  rock  fragments  and  lapilli.  No  heavy  boulders  were  thrown  beyond  the 
crater  rim,  no  bombs  or  fragments  showing  signs  of  recent  fusion,  and  no  fragments 
hot  enough  to  melt  the  snow  so  long  as  there  was  snow  where  they  fell.  Later  in 
the  season  when  the  forest  carpet  in  the  vicinity  consisted  of  dry  leaves  of  highly 
inflammable  character  no  fires  were  set  by  ejected  material. 

This  evidence,  when  brought  together,  plainly  indicates  that  during  the  first 
year  of  activity  (1914  and  the  winter  of  1915)  there  were  no  evidences  of  chemical 


32 


action,  of  high  temperature,  or  of  the  development  of  great  volcanic  power.  Neither 
was  there  during  this  period  any  dislodgment  of  any  portion  of  the  mountain  struc¬ 
ture  beyond  the  original  east-and-west  rift,  or  of  heavy  boulders. 

It  is  pertinent,  and  perhaps  significant,  to  note  that  a  considerable  body  of 
snow  within  the  crater  basin  melted  and  disappeared  in  cracks  leading  down  to  the 


Fig.  23. — Explosions  in  quick  succession  in  summer  of  1914.  Photo  Mullen. 


center  of  activity  during  the  early  weeks  of  the  eruptions.  The  water  thus  assimi¬ 
lated  certainly  participated  in  the  steam  explosions,  but  whether  or  not  as  a  con¬ 
tributory  cause  will  perhaps  better  be  left  to  a  later  chapter  for  discussion.  Diller, 
who  has  also  commented1  upon  this  fact,  has  discarded  it  as  an  essential  factor  in  the 
activity,  because  the  explosions  continued  (fig.  25),  with  generally  increasing 


Unpublished  communication. 


33 


violence  throughout  the  summer  months  long  after  the  snow  had  disappeared. 
This  fact,  however,  may  indicate  merely  that  the  explosions  were  not  so  simple 
a  matter  as  pouring  a  mass  of  water  into  a  hot  cavern  and  witnessing  the  immediate 
explosion  of  it  as  steam.  Indeed,  if  the  operation  of  the  volcano  had  been  as 
simple  as  this  we  should  not  have  had  separate  explosions  at  intervals  of  several 
days  during  the  period  of  melting  snow,  but  a  more  or  less  continuous  discharge  of 
steam  (during  the  daytime  at  least)  until  all  the  snow  was  melted,  followed  by  a 
cessation  of  activity  until  the  following  spring.  The  fact  that  no  such  simple 
mechanism  was  discovered  in  no  wise  disposes  of  the  participation  of  water  in  the 
activity  at  Lassen  Peak.  Great  quantities  of  water  actually  flowed  into  the 
explosion  crater  and  its  tributary  cracks,  as  observed  by  the  forest  rangers  and 
many  others,  and  great  quantities  reappeared  in  the  explosions.  There  is  no 
evidence  that  the  activity  was  damped  thereby;  on  the  contrary  it  increased 


Fig.  26. — August  10,  1915.  Summit,  looking  west  along  the  south¬ 
ern  edge  of  the  upheaved  plug.  Photo  Diller. 


rapidly  during  this  period,  both  in  intensity  and  duration.  The  participation  of 
the  water  in  this  activity  therefore  constitutes  one  of  the  chief  problems  offered  by 
Lassen  Peak  during  this  eruption.  It  requires  laboratory  study  for  its  elucidation, 
however,  and  will  therefore  be  discussed  more  in  detail  on  a  later  page. 

SECOND  PERIOD  OF  ACTIVITY,  MAY,  1915. 

As  has  been  indicated  in  the  preceding  description,  the  first  sign  of  the  change 
in  the  character  of  the  activity  at  the  close  of  the  first  period  was  indicated  by  the 
observations  of  Loomis  and  Miss  Dines  a  day  or  two  previous  to  the  great  eruption 
of  May  19  and  22.  These  observers  noted  (p.  15)  the  appearance  of  a  black  mass 
thrust  up  into  the  western  notch  on  the  summit,  which  suggested  to  them,  and  may 
well  have  been,  an  upheaval  of  the  whole  bottom  of  the  old  crater  bowl  (fig.  26), 
completely  filling  the  explosion  crater,  which  had  grown  during  the  previous  year 
to  occupy  nearly  the  whole  of  this  bowl.  The  last  estimate  of  the  size  of  the  explo¬ 
sion  crater  reported  it  to  be  nearly  round  and  about  1,000  feet  in  diameter  (March 


34 


1915)-  Its  depth  was  never  measured,  nor  did  any  observer  from  June  1914  to 
March  1915  take  note  of  any  exposure  of  the  solid  bottom,  other  than  the  point  of 
meeting  of  the  talus  from  the  surrounding  walls.  In  other  words,  the  explosion 
crater  during  the  first  period  was  always  approximately  an  inverted  cone,  at  first 
narrow  and  afterward  broadening  out  as  the  explosions  continued  and  removed  the 
loose  material  out  to  the  inclosing  rim  of  the  bowl.  These  explosions  of  the  first 
period,  then,  apparently  failed  to  reach  solid  rock,  still  less  molten  magma.  The 
observations  of  Loomis  and  Miss  Dines  therefore  offer  the  first  clue  to  the  appear¬ 
ance  in  action  of  the  greater  forces  through  which  the  volcano  plug  was  lifted  at 
least  300  feet,  and  perhaps  much  more  than  this,1  and  which  found  release  after¬ 
ward  in  the  two  mighty  explosions  of  May  19  and  22,  1915. 

These  explosions  were  of  very  considerable  intensity.  The  first  (May  19) 
came  in  the  night  and  so  brought  to  view  the  only  incandescent  lava  certainly 
observed  on  the  mountain  during  its  activity.  By  virtue  of  this  observation  we 
have  a  clue  to  the  crater  temperature  while  the  activity  was  at  its  maximum.  The 
second  of  the  great  explosions  occurred  during  daylight  and  so  enabled  the  Forest 
Service  observers  to  estimate  by  triangulation  the  height  of  the  dust  cloud  accom¬ 
panying  the  blast  (25,000  feet  above  the  summit).  Associated  with  each  of  these 
great  explosions  was  one  or  more  horizontal  blasts  of  tremendous  destructive  power, 
suggesting  the  nuees  ardentes  of  Lacroix  at  Martinique.  These  outbursts  were 
heavily  charged,  both  with  dust  and  heavier  detritus  and  with  water  vapor,  which 
together  were  sufficient  to  melt  completely  the  snow  in  their  pathway  and  so  to 
cause  destructive  floods  which  submerged  the  valleys  of  Lost  Creek  and  Hat  Creek 
to  a  depth  of  Irom  2  to  10  feet  for  some  20  miles.  It  will  also  be  recalled  that  these 
blasts  carried  away  or  laid  down  in  a  single  direction,  pointing  away  from  the 
mountain,  standing  timber  up  to  5  feet  in  diameter,  far  above  any  level  reached  by 
the  flood;  that  they  were  hot  enough  to  singe  but  not  to  fire  the  foliage  of  the 
evergreens,  and  that  the  flood  material  when  allowed  to  settle  yielded  something  like 
90  per  cent  of  solid  matter  (including  pore-space).  We  shall  consider  these  facts 
in  some  detail  in  the  subsequent  discussion. 

Following  this  culminating  outbreak  a  normal  subsidence  period  ensued, 
covering  altogether  a  period  of  about  2  years,  in  which  the  activity  only  once  (May 
1917)  attained  to  any  considerable  intensity.  The  only  noteworthy  feature  of  this 
period  for  purposes  of  a  discussion  of  causes  is  the  date  of  the  renewal  of  the  violent 
explosions  (May  18,  1917),  which  corresponds  very  closely  to  the  date  of  the  first 
outbreak  (May  30,  1914)  and  to  the  height  of  the  activity  (May  22,  1915). 

In  type  the  present  outbreak  was  a  mild  and  but  incipiently  developed  counter¬ 
part  of  the  eruption  of  Mont  Pelee  (Martinique)  in  1902.  A  great  number  of  ex¬ 
plosions  occurred,  causing  violent  displacements  of  old  material  within  the  crater 
and  an  eventual  upheaval  (May  1915)  of  the  entire  crater  floor,  but  these  disturb¬ 
ances  did  not  lead  to  a  lava  flow,  nor  were  they  sufficient,  as  in  the  case  of  Bandai- 

1  300  feet  represents  merely  the  difference  in  level  between  the  bottom  of  the  old  crater  bowl  (before  1914)  and  the 
elevation  of  the  top  of  the  plug  after  the  upheaval  (May  1915).  The  depth  of  the  debris  overlying  the  solid  plug  before  the 
upheaval  is  of  course  unknown,  the  amount  of  this  debris  scattered  over  the  countryside  during  the  hundred  and  more 
explosions  of  the  first  year,  before  the  upheaval,  would  indicate  that  it  was  considerable. 


35 


san,  to  destroy  or  blow  off  the  top  of  the  mountain.  There  is  also  this  further 
difference,  that  the  violence  of  the  explosions  of  Bandai-san  was  sufficient  to  relieve 
the  pressure  within  the  mountain  in  rather  less  than  an  hour,  and  the  eruption  had 
practically  spent  itself  within  that  time.  The  explosions  at  Lassen  Peak  continued 
intermittently  through  nearly  5  years,  no  one  of  them  being  sufficiently  violent  to 
alter  radically  the  shape  of  the  mountain  or  to  remove  any  considerable  volume  of 
matter  from  the  crater  basin  (like  the  great  Katmai  eruption  of  1912  for  example, 
when  about  a  cubic  mile  of  the  mountain  top  and  crater  basin  was  blown  away). 
In  point  of  violence,  therefore,  compared  with  the  great  explosions  of  history, 
Lassen  Peak  showed  only  moderate  activity  at  any  time,  although  during  the 
second  year  there  were  two  explosions  (May  19  and  22)  of  sufficient  violence  to 
have  overwhelmed  a  small  city  (like  St.  Pierre,  Martinique)  in  case  it  had  happened 
to  be  located  in  Lost  Creek  Valley.  Accompanying  the  May  eruption  in  1915 
there  was  an  upheaval  of  the  crater  floor  which  penetrated  through  the  rim,  both 
east  and  west,  for  a  total  length  of  about  2,000  feet,  and  rising  at  its  highest  point 
some  300  feet  above  the  original  floor-level,  but  only  random  fragments,  and  these 
practically  all  at  the  eastern  notch,  were  projected  beyond  the  mountain  top.  A 
few  of  these  boulders  weighed  several  tons. 


CHAPTER  II. 

CHEMICAL  AND  PHYSICAL  RELATIONS  (Laboratory  Study). 

CHEMICAL  COMPOSITION.1 

Perhaps  no  North  American  volcano  has  been  so  extensively  studied  chemically 
as  Lassen  Peak.  Detailed  field  investigations,  of  somewhat  limited  scope,  to  be 
sure,  have  also  been  carried  to  a  stage  of  admirable  completeness.  Unfortunately, 
however,  little  has  been  done  in  the  detailed  description  of  the  volcanic  products, 
and,  although  the  materials  are  available  and  await  use,  an  adequate  petrological 
interpretation  of  the  field  has  yet  to  appear.  Several  andesites  and  dacites  and  a 
number  of  pyroclastic  products  have  been  described,2  and  Diller  has  made  a 
detailed  study  of  the  quartz  basalt  of  Cinder  Cone,3  while  Hague  and  Iddings 
provide  some  generalized  descriptions  of  the  lavas.4  Desirable  detail  on  the  order  of 
succession  and  the  mineralogical  and  textural  variety  of  the  rock  types,  however,  is 
lacking.  Of  the  mineral  phases  produced  we  know  practically  nothing,  the  only 
mineral  analysis  being  that  of  a  plagioclase  which  contains  glassy  inclusions. 

We  possess  now  some  55  analyses  of  rocks  from  the  Lassen  field,  of  which  7  are 
tuffs  and  5  are  “secretions”  in  lava  flows.  The  remainder  consists  of  6  rhyolites, 
8  dacites,  14  andesites,  8  quartz  basalts,  and  5  basalts  from  the  regional  suite, 
together  with  1  hornblende  basalt,  mentioned  above,  and  1  pumice,  which  are  so 
exceptional  in  character  and  occurrence  that  in  all  probability  they  do  not  belong 
to  the  Lassen  magmatic  series  at  all.  Nearly  all  of  the  analyses  are  of  excellent 
quality,  and  most  of  them  have  been  published  by  the  United  States  Geological 
Survey.5  They  enable  certain  conclusions  to  be  drawn. 

If  the  analyses  of  the  lavas  be  arranged  and  examined  critically  they  are  found 
to  represent  five  well-defined  groups,  corresponding  to  the  five  types:  rhyolite, 
dacite,  andesite,  quartz  basalt,  and  basalt.  The  “secretions”  demand  separate 
treatment.  The  lavas,  as  Harker  has  shown,6  form  a  graded  series,  but  whereas  he 
considered  that  the  quartz  basalts  do  not  fit  well  into  the  serial  arrangement,  we 
find  that  in  general  they  show  divergence  of  serious  magnitude  only  in  being  low  in 
alumina  and  high  in  magnesia  (the  oxides  chosen  by  Harker  to  demonstrate  the 
exception).  The  only  other  notable  difference  is  in  their  low  water  content.  They 
fit  the  scheme,  indeed,  quite  as  well  as  the  so-called  “secretions,”  which  are  high  in 
alumina  and  low  in  lime.  The  fact  that  the  silica  range  of  the  “secretions”  embraces 
that  of  the  quartz  basalts  is  suggestive  of  some  relationship  between  them.  Arrang- 

1  With  the  co-operation  of  Mr.  Aurousseau. 

2  U.  S.  Geol.  Surv.  Bull.  150,  1898. 

3  J.  S.  Diller,  A  late  volcanic  eruption  in  Northern  California,  U.  S.  G.  S.  Bull.  79,  1891. 

4  A.  Hague  and  J.  P.  Iddings,  Notes  on  the  volcanoes  of  Northern  California,  Oregon,  and  Washington  Territories,  Am. 

Journ.  Sci.  (3),  25,  222-235.  1883. 

6  H.  S.  Washington,  Chemical  analyses  of  igneous  rocks,  U.  S.  Geol.  Surv.,  Prof.  Paper  99,  1917;  U.S.  Geol.  Surv.  Bull. 
148,  191-200,  1897;  Bull.  591,  169-175,  1915. 

0  A.  Harker,  The  natural  history  of  igneous  rocks,  1909,  pp.  125,  355,  figs.  28,  no. 

36 


37 


ing  the  lavas  in  the  order  of  their  silica  percentages,  the  five  types  are  found  to  be 
characterized  by  a  well-defined  silica  range,  and  are  generally  separated  by  signifi¬ 
cant  gaps.  The  rhyolite  range  is  well  separated  from  that  of  dacite  and  is  un¬ 
bridged.  That  of  dacite  is  well  separated  from  andesite.  The  andesite  range  is 
comparatively  wide  and  overlaps  that  of  quartz  basalt,  but  it  and  that  of  quartz 
basalt  are  well  marked  off  from  true  basalt.  The  ‘'secretions”  embrace  the  quartz 
basalt  range  and  overlap  that  of  andesite,  but  not  that  of  basalt.  The  analyses  for 
each  type  group  of  rocks  were  accordingly  averaged  and  the  results  recalculated  to 
ioo  per  cent,  as  shown  in  table  i. 


Fable  i. — Average  composition  of  the  dominant  rock 
types,  Lassen  Peak. 


1 

2 

3 

4 

5 

6 

SiO« . 

73.73 

68.41 

60.89 

56.25 

55.34 

51  .24 

A 1  ( )s . 

14.05 

16.02 

16.90 

16.79 

18.80 

18.17 

Fe20» . 

0.99 

1 .76 

2.77 

1 .70 

3.92 

4.19 

FeO . 

0.59 

1  .14 

2.75 

4.84 

3.18 

4.81 

MgO . 

0.29 

1 .28 

3.13 

6.54 

5 .13 

6.29 

CaO . 

1 .04 

3.20 

6.45 

7.90 

7.54 

9.90 

Na,0 . 

3.30 

4.08 

3.79 

3.26 

3.20 

2.80 

k,o . 

4.23 

2.60 

1  .65 

1  .31 

1  .22 

0.73 

1 1.0 . 

1 .36 

1 .00 

0.81 

0.52 

0.90 

0.99 

TiO, . 

0.18 

0.24 

0.53 

0.54 

0.51 

0.55 

P2O5 . 

0.04 

0.10 

0.15 

0.17 

0.10 

0.17 

MnO . 

0.08 

0.09 

0.11 

0.13 

0.12 

0.15 

BaO . 

0.11 

0.06 

0.04 

0.03 

Trace 

0.01 

SrO . 

0.01 

0.02 

0.03 

0.02 

0.04 

trace 

Li.,0 . 

Trace 

Trace 

Trace 

Trace 

Trace 

None 

Sum . 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

1.  6  rhyolites.  Silica  range,  74.65  to  72.40  per  cent. 

2.  8  dacites  (includes  2  “andesites”).  Silica  range,  69.51  to  67.89  per  cent. 

3.  14  andesites  (includes  1  “dacite”).  Silica  range,  63.81  to  55.20  per  cent.  Water  range  of  12  analyses,  1.24  to  0.51  per 

cent. 

4.  8  quartz  basalts.  Silica  range,  57.59  to  54.56  per  cent.  Water  range  of  5  analyses,  0.42  to  0.27  per  cent. 

5.  5  “secretions”  in  dacites  and  andesites.  Silica  range,  58.97  to  53.35  per  cent.  All  notably  rich  in  alumina. 

6.  5  basalts.  Silica  range,  52.95  to  47.93  per  cent. 

The  serial  relations  are  admirably  shown  by  the  average  type  values  and  have 
been  plotted  as  a  variation  diagram  (fig.  27).  It  is  noteworthy,  in  comparing  this 
diagram  with  the  “smoothed”  curves  of  Harker  (another  method  of  averaging, 
which  should  lead  to  identical  diagrammatic  results),1 2 3 4 5 6  that  the  forms  of  the  individ¬ 
ual  curves  differ  somewhat  at  the  basic  end.  This  is  doubtless  due  to  the  tact  that 
he  has  included  in  his  diagrams  the  hornblende  basalt,  which  we  regard  as  ex¬ 
traneous.  The  figures  for  this  rock  and  the  pumice  differ  so  greatly  from  those  of 
the  undoubted  products  of  the  Lassen  field,  that  they  must  of  necessity  displace  the 
average  figures  of  basalt  considerably.  The  mineral  character  and  single  occur¬ 
rence  of  the  hornblende  basalt  throw  suspicion  upon  it,  and  the  pumice  is  not  only 
exceptionally  silicic,  but  shows  low  alumina,  and,  contrary  to  expectation,  high  lime 
and  reversed  alkali  values.  Its  water  content  is  low  (perhaps  not  a  significant 


1  A.  Harker,  The  natural  history  of  igneous  rocks,  1909,  pp.  125,  355,  figs.  28,  no. 


38 


S3Q  1X0  33H.L0  30  30V-LN3D33d 


Fig.  27. — Curves  showing  the  variations  in  the  composition  of  the  Lassen  Peak  Rocks.  Constructed  from  the  type  averages 
of  Table  I . 


39 


point)  and  it  contains  no  manganese.  In  every  way  it  is  exceptional,  and  we  ex¬ 
clude  it  from  membership  in  the  Lassen  suite. 

The  Lassen  rocks  on  the  whole  show  some  interesting  individual  features  for 
the  field,  which  link  it  with  such  areas  as  Shasta,  Crater  Lake  (Oregon),  and 
inferentially,  with  Mount  Hood  and  Mount  Rainier.  It  can  hardly  be  doubted  that 
these  great  volcanoes  have  all  had  a  similar  magmatic  history  and  express  similar 
processes  in  the  production  of  their  lavas.1  The  Lassen  rocks  are  normally  alkali- 
calcic,  and  only  in  the  range  of  their  minor  constituents  do  they  differ  from  similar 
andesites,  dacites,  etc.,  from  other  parts  of  the  world.  Their  Ti02  content  is  a 
little  lower  than  usual.  They  contain  notable  amounts  of  BaO,  especially  towards 
the  silicic  pole,  which  preponderates  as  a  rule  over  an  ever-present  but  small 
amount  of  SrO.  All  contain  traces  of  Li20,  but  Zr02  is  present,  where  it  has  been 
sought,  only  in  the  smallest  amounts,  and  P205  throughout  the  suite  is  in  smaller 
amount  than  is  usual.  MnO  is  present  in  normal  quantity.  Cl,  F,  and  S,  if  present, 
exist  in  quantities  barely  determinable  by  gravimetric  methods.  The  values  for 
H20  deserve  close  inspection  in  relation  to  the  last  products  of  eruption  (1915). 
Only  in  the  quartz  basalts  do  they  fall  below  0.50  per  cent.  In  all  the  other  rocks 
water  is  present,  usually  in  amounts  well  above  this  value.  These  minor  characters 
are  also  to  be  seen  in  the  published  analyses  of  rocks  from  Shasta  and  Crater  Lake, 
Oregon. 

The  “secretions”  do  not  fit  the  variation  diagram.  Diller  regards  them  as 
products  of  early  crystallization  in  the  rocks  in  which  they  occur.2  They  are 
notably  high  in  alumina,  a  little  low  in  lime,  and  exhibit  small  but  notable  amounts  of 
strontia.  Their  alkali  content  is  close  to  that  of  the  types  of  the  suite. 

Little  can  be  said  concerning  the  nature  of  the  processes  of  differentiation  in 
the  Lassen  field,  except  that  from  the  diversity  of  rocks  produced  they  must  have 
proceeded  nearly  to  completion.  Hague  and  Iddings  have  published  two  interesting 
tables  of  analyses  which  suggest  how  crystallization  affects  the  composition  of  the 
remaining  magma.  In  a  pumice  from  Shasta  they  give  analyses  of  the  rock,  its 
hypersthene,  feldspar,  and  glass;  in  a  dacite  from  Lassen,  the  rock,  the  feldspar, 
and  the  glass  are  given.1  In  both  examples  the  glass  is  highly  silicic  and  the 
greater  part  of  the  potash  is  concentrated  in  it.  We  have  calculated  the  analysis  of 
the  feldspar  (which  contains  glassy  inclusions)  from  the  Lassen  dacite.  It  is  as 
shown  herewith: 


Quartz . 

....  16.08 

Alumina . 

....  0.50 

Orthoclase . 

.  5  -°o 

Albite . 

....  49  78l 

Anorthite . 

-  28.36/ 

Water . 

.  0.34 

100.06 

1  A.  Hague  and  J.  P.  Iddings,  Notes  on  the  volcanoes  of  Northern  California,  Oregon  and  Washington  Territories,  Am. 
Journ.  Sci.  (3),  23,  222-233,  1883. 

2U.  S.  Geol.  Surv.  Bull.  150,  1898. 


40 


These  interesting  results  suggest  that  towards  the  silicic  pole  the  process  has 
proceeded  from  the  basic  side  to  the  production  of  silicic  types.  The  ‘"glass”  of 
the  dacites  may  well  correspond  to  the  composition  of  the  rhyolites.  This  early 
chemical  work  is  an  attempt  at  phase  analysis,  and  merits  attention. 

PRODUCTS  OF  RECENT  ACTIVITY. 

The  recent  activity  of  Lassen  Peak  has  been  characterized  by  the  eruption  of  ash, 
the  evolution  of  steam,  and  on  May  19  to  22,  1915,  by  the  filling  of  the  crater  with 
lava  from  below  (the  uplifted  plug).  We  propose  to  examine  critically  the  material 
extruded  in  this  latest  upheaval  on  external,  internal,  and  experimental  grounds,  in 
order  to  ascertain  if  it  presents  any  evidence  on  the  mechanism  of  the  recent  activity. 

From  the  general  considerations  of  the  preceding  sections,  Lassen  Peak  may 
be  interpreted  as  an  old  and  dying  volcano.  It  has  extruded  the  products  charac¬ 
teristic  of  a  very  well-differentiated  magma,  and  its  greatest  period  of  activity  has 
long  since  passed.  Occasional  outbursts  of  no  great  violence  may  still  be  expected, 
the  most  likely  product  of  which  would  be  comminuted  ash  due  to  attrition  in  the 
choked  vent,  with  a  moderate  discharge  of  steam  and  rising  gases.  If  magmatic 
material  in  sufficient  quantity  to  produce  a  lava  flow  still  exists  beneath  the  cone, 
the  recent  history  of  Cinder  Cone,  and  the  stage  ol  differentiation  attained,  would 
lead  one  to  expect  the  eruption  of  a  lava  resembling  the  products  of  the  later 
stages  of  activity,  a  rock  of  more  extreme  type  than  the  extrusions  of  the  opening 
or  most  active  phases  (andesite) — a  quartz  basalt  or  even  a  normal  basalt  would 
not  be  astonishing.  The  behavior  of  the  Cinder  Cone  suggests  that  it  is  not  im¬ 
probable.  Lassen  Peak  itself  consists  ot  dacite  on  the  northeast,  which  embraces 
the  crater,  of  pyroxene  andesite  on  the  southwest,  with  normal  basalt  on  the  lower 
flanks  all  around,  and  an  area  of  rhyolite  on  the  low  western  flank.  A  mile  north  of 
the  crater  is  a  very  small  area  of  quartz  basalt. 

The  real  products  of  the  recent  eruption,  however,  differ  considerably  from 
what  might  have  been  expected.  The  ash  is  andesitic,  or  dacitic,  in  composition, 
while  the  uplifted  and  shattered  plug  is  an  andesite  of  somewhat  variable  com¬ 
position,  exhibiting  three  significant  physical  modifications,  having  in  the  main  the 
chemical  composition  of  some  of  the  old  andesitic  or  dacitic  rocks  which  form  the 
northeastern  part  of  the  upheaved  mass  and  the  inclosing  crater  of  Lassen  Peak 
itself.  The  composition  of  the  ash  and  of  two  forms  of  the  lava  which  now  fill  the 
crater,  together  with  an  analysis  of  the  youngest  dacite  of  the  region  (according  to 
Diller),  are  given  in  table  2. 

The  ash,  dust,  and  pumice  of  the  recent  eruptions  covered  the  country  to  the 
northeast  of  Lassen  Peak.  That  analysed  by  Shepherd  was  collected  from  the  Hat 
Creek  “mud  flow”  in  June  1915.  It  was  air-dried,  that  is,  it  remained  in  a  screw- 
capped  glass  jar  until  analysed  in  1923.  The  analysis  (No.  2  of  table  2)  shows  no 
peculiarities  except  a  slightly  higher  amount  of  silica  than  would  be  expected  from 
the  composition  of  the  lava.  Physically  this  mud  flow  consists  of  fine  ash,  mixed 
with  fragments  of  two  modifications  of  the  andesite  of  the  new  lava.  These  coarser 
fragments  were  removed  by  passing  the  material  through  a  28-mesh  sieve.  Of  the 


41 


Table  2. 


1 

2 

3 

4 

5 

SiOo . 

63.86 

66.45 

63.21 

64.16 

68.72 

A 14), . 

16.07 

16.19 

17.15 

16.87 

15.15 

Fe20, . 

1  .56 

2  .66 

1 .30 

1  .46 

1 .16 

FeO . 

2.31 

1 .12 

3.00 

2  .77 

1 .76 

MgO . 

2.11 

1  .86 

2.96 

2.60 

1  .28 

CaO . 

4.94 

4.55 

5  .23 

4.96 

3  .30 

Na-0 . 

3.59 

4.06 

4.12 

4.09 

4.26 

K.,0 . 

1  .91 

2.03 

2.10 

2.29 

2.78 

H20+ . 

H.O— . 

0.81 

1  .47 

0.68 

0.39 

0.31 

0.04 

0.13 

0.05 

j  0.74 

CCL .  . 

none 

none 

Tid . 

0.45 

0.39 

0.48 

0.55 

0.31 

ZrO, . 

0.04 

0.01 

0.02 

trace 

p.,o6 . 

0.12 

0.16 

0.16 

0.12 

0.09 

Cl . 

0.02 

n.d. 

F.  . 

p.n.d.1 2 3 4 5 

0.03 

p.n.d.1 

0.02 

S . 

0.84 

0.09 

Cr.O, . 

none 

none 

MnO . 

0.05 

0.10 

0.07 

0.08 

0.11 

BaO  . 

0.03 

0.07 

0.07 

0.07 

SrO  . 

0.03 

LEO..  . 

trace 

trace 

Sum . 

Less  0 . 

100.16 

100.33 

0.04 

100.27 

0.01 

100.22 

99.76 

Sum . 

100.16 

100.29 

100.26 

100.22 

99.76 

Norms  of  3  and  4. 


3 

4 

Quartz . 

15 .18 

17.28 

Orthoclase . 

12.23 

13.34 

Albite . 

34.58 

34.58 

Anorthite . 

22  .24 

21.13 

Diopside . 

2.26 

1.63 

Hypersthene . 

10.00 

8.57 

Ilmenite . 

1 .06 

1  .06 

Magnetite . 

1  .86 

2  .09 

Apatite . 

0.34 

0  .34 

Water . 

0.35 

0.28 

Sum . 

100.10 

100.30 

Symbols . 

I(II).  4 ".3.4. 

I  (II)  .4.3.4. 

Name . 

Y  ellowstonose 

Yellowstonose 

1.  Andesitic  ash,  Lassen  Peak,  September  1914.  U.  S.  Geol.  Surv.,  Prof.  Pap.  99,  p.  259.  W.  C.  Wheeler,  analyst. 

2.  Andesitic  ash.  Hat  Creek  mud  flow,  eruption  of  1915,  Lassen  Peak.  E.  S.  Shepherd,  analyst. 

3.  Pyroxene  andesite  (dacitic).  Dense,  glassy  variety.  The  crater,  Lassen  Peak.  Eruption  of  1915.  Collected  by 
E.  T.  Allen,  June  1922.  M.  Aurousseau,  analyst. 

4.  Pyroxene  andesite  (dacitic).  Pumiceous  variety.  4  he  crater,  Lassen  Peak.  Eruption  of  1915.  Collected  by  E.  I. 
Allen,  1922.  M.  Aurousseau,  analyst. 

5.  Dacite.  East  end  of  Chaos,  northwest  base  of  Lassen  Peak.  The  youngest  dacite  of  the  region.  J.  S.  Diller,  U.  S, 
Geol.  Surv.,  Bull.  150,  p.  218,  1898.  W.  F,  Hillebrand,  analyst. 

1  Present — Not  determined. 


42 


remaining  portion  about  half,  by  volume,  passes  through  the  125-mesh  bolting 
cloth  without  further  grinding.  Microscopically  this  powder  is  distinguishable  from 
the  powdered  andesite  (vesicular  variety)  only  in  the  obvious  presence  of  slightly 
more  quartz.  It  is  a  mixture  of  glassy  material  containing  small  crystals  ol  feldspar 
and  pyroxene,  broken  grains  of  feldspar  phenocrysts,  and  occasional  grains  of 
magnetite  and  shreds  of  biotite.  Apparently  this  material  is  merely  comminuted 
andesite  (vesicular  variety)  from  the  lava  in  the  conduit.  In  passing,  it  may  be 
noted  that  the  grains  of  magnetite  and  shreds  of  biotite  appear  identical  with  the 
biotite-magnetite  relations  in  the  andesite.  The  main  mass  of  the  “mud  flow,” 
as  well  as  the  great  quantities  of  ash  and  pumice  which  covered  the  country  to  the 
northeast,  seem  to  have  been  of  this  material.  The  ash  of  1914  agrees  more  closely 
with  the  andesite  of  the  volcano  plug  (1915)  in  composition,  the  differences  in  the 
two  analyzed  samples  of  ash  being  due  perhaps  to  the  sorting  effect  of  the  atmos¬ 
phere.  The  presence  of  so  large  an  amount  of  free  sulphur  in  Wheeler’s  sample  is  of 
no  particular  significance,  in  view  of  the  fact  that  we  do  not  know  its  local  origin, 
but  the  differences  in  the  iron  values  are  interesting.  Wheeler’s  sample  is  practically 
a  comminuted  form  of  the  andesite.  The  Hat  Creek  sample  suggests  a  preponder¬ 
ance  of  magnetite. 

The  andesite  of  the  lava  of  1915,  which  partly  filled  the  crater  and  intersects 
the  rim  on  the  western  side,1  is  a  dacitic  rock,  an  andesite  containing  insignificant 
amounts  of  free  quartz,  a  little  biotite,  and  a  little  pyroxene.  It  is  very  variable 
in  composition  and  shows  three  distinct  physical  modifications — a  dense  andesite, 
a  pumiceous,  and  a  bread-crust  variety.  The  crater  was  rifted  east  and  west2  and 
the  i,ooo-foot  tongue  of  lava,  which  transgresses  the  rim,  occupies  the  western 
notch  of  the  rift.  From  the  general  nature,  disposition,  and  appearance  of  the  lava 
it  is  the  top  of  a  mass  of  material  (the  “plug”)  which  has  risen  in  the  vent  to  the 
level  of  the  old  crater  rim,  convex  in  general  form,  crusted  and  solidified  above,  and 
capable  of  viscous  movement  below.  In  expanding  to  fill  the  larger  diameter  of  the 
upper  part  of  the  crater  and  the  rift  on  the  west,  the  upper  crust  has  been  cracked 
and  fissured  vertically  as  the  viscous  lower  portions  pushed  it  upward. 

The  modification  of  this  lava,  which  we  term  the  dense,  glassy  andesite,  is  a 
black  rock,  containing  abundant  glistening  phenocrysts  of  plagioclase.  It  has  a 
smooth  fracture.  The  color  is  the  neutral-gray  M  of  Ridgway.  With  the  white 
plagioclase  phenocrysts,  which  range  up  to  8  by  15  mm.  in  size,  a  little  free  quartz, 
a  rare  flake  of  biotite,  and  an  occasional  phenocryst  of  pyroxene,  perhaps  7  mm.  long, 
may  be  seen.  Apparently  rolled  into  it  are  occasional  inclusions  from  which  the  lava 
has  more  or  less  pulled  away.  One  specimen  shows  a  wrinkled  surface  and  an 
abortive,  laminated  mass-structure  which  suggests  its  having  been  rubbed  along  a 
colder  or  more  rigid  mass,  or  that  the  nearly  rigid  material  has  been  fractured;  other¬ 
wise  it  resembles  all  the  specimens  of  the  dense  material  in  showing  flow  while  in  an 
almost  rigid  condition,  which  came  little  short  of  fracture.  All  of  the  dense, 

1  J.  S.  Diller,  Lassen  Peak — our  most  active  volcano,  Bull.  Seismol.  Soc.  Am.  6,  1-7,  1916. 

2  A.  L.  Day,  Possible  causes  of  the  volcanic  activity  at  Lassen  Peak,  Bull.  Seismol.  Soc.  Am.,  12,  35-46,  1922; 
Journ.  Franklin  Inst.  194,  569-582,  1922. 


43 


glassy  material  examined  is  shattered  throughout  in  a  peculiar  manner;  a  network 
of  minute  cracks  divides  the  mass  into  cells  about  0.5  cm.  in  diameter.  While 
not  noticeable  on  first  inspection,  a  smooth  or  polished  surface,  when  wetted,  will 
in  drying  show  the  cracks  distinctly.  The  fracturing  is  not  pronounced  enough  to 
prevent  cutting  4  mm.  slices  of  the  rock,  but  it  is  quite  definite.  The  feldspar 
phenocrysts  are  all  shattered  and  easily  broken  out,  and  those  of  pyroxene  are 
fractured.  Apparently  the  dense,  glassy  andesite  occurs  chiefly  near  the  source  of 
the  extrusion,  or  in  angular  blocks  thrown  out  and  scattered  about  the  mountain- 
top.  Dr.  Fenner  (in  1919)  found  one  piece,  apparently  of  this  material,  showing 
the  transition  from  dense  to  vesicular  structure  on  the  top  of  Cinder  Cone,  10  miles 
distant  from  Lassen  Peak.  In  all  respects  it  suggests  flow  under  pressure  while  in 
a  viscous,  almost  rigid  state.  Whether  any  portion  of  the  upheaved  plug  now 
exposed  was  actually  viscous  during  the  eruptive  period  1914-17,  or  the  fragments 
showing  indications  of  viscous  movement  belong  to  an  earlier  period  of  activity,  it  is 
not  possible  to  say  with  certainty  on  account  of  its  shattered  and  disconnected  con¬ 
dition.  As  far  as  is  known,  however,  all  of  the  newly  erupted  material  consists  of 
one  or  another  phase  of  this  parent  andesite,  or  dacite. 

Microscopic  examination  shows  the  dense  andesite  to  be  variable  in  composi¬ 
tion.  It  may  contain  from  40  to  60  per  cent  of  glass,  according  to  the  specimen 
examined.  An  estimate  of  the  amounts  of  plagioclase,  biotite,  pyroxene,  and 
quartz  occurring  as  phenocrysts  gave  the  respective  proportions  15  :  3  :  2  :  less  than 
1.  Magnetite,  in  minute  grains,  is  the  only  noteworthy  accessory. 

The  plagioclase  is  partly  fragmentary  and  mostly  rounded.  It  shows  successive 
reaction  surfaces  and  irregular  zoning  with  less  and  more  calcic  material  alternat¬ 
ing.  The  more  calcic  material  often  penetrates  along  a  fracture  line  through  a 
zoned  crystal.  The  narrow  outer  zones  of  the  phenocrysts  are  sharply  marked  and 
notably  more  calcic  than  the  neighboring  inner  ones,  but  they  show  resorption. 
The  range  of  composition,  as  determined  by  refractive  indices  on  powder,  varies 
between  Ab2  An,  and  Ab3  An2.  None  of  the  phenocryst  feldspar  is  as  calcic  as 
some  of  that  of  the  ground-mass. 

The  biotite  is  always  surrounded  by  a  border  of  reaction  products  1  and  for  the 
most  part  is  decomposing,  as  might  be  expected  in  a  conduit  plug  which  may  have 
been  reheated  several  times.  This  decomposition  results  in  the  grains  of  magnetite 
noted  in  the  ash  of  the  Hat  Creek  mud  flow,  and  explains  the  ferrous-ferric  ratio  of 
the  analysis  of  the  ash.  Biotite  separated  from  the  rock  magnetically  showed 
optical  characteristics,  undoubtedly  due  to  loss  of  volatiles  and  partial  oxidation 
(as  will  be  explained  below).  It  gave  7=1.68  to  1.7c,  with  2E=io°  to  40°,  and 
showed  varying  degrees  of  reddening.  The  pyroxene  is  neardiopside  in  composition, 
having  «=  1-675,  and  7=  1.715.  It  usually  occurs  in  granular  aggregates  as  though 
shattered.  A  few  grains  of  quartz  occur,  their  corrosion  being  the  only  point  of 
interest. 

The  ground-mass  is  a  brownish  glass  in  which  both  plagioclase  and  pyroxene 
needles  are  abundant,  but  orthoclase  is  absent.  Most  of  the  plagioclase  needles  are 


1  Cf.  H.  S.  Washington,  The  magmatic  alteration  of  hornblende  and  biotite,  Journ.  Geol.,  4,  257-282,  1896. 


44 


more  calcic  than  any  of  the  phenocrysts,  reaching  Ab2An3  in  composition.  The 
glass  is  brownish  by  transmitted  light  and  full  of  minute  microscopic  crystals. 
It  is  highly  siliceous,  with  a  refractive  index  varying  greatly  over  short  distances 
from  1.485  to  1.500,  and  is  thus  notably  inhomogeneous. 

The  composition  of  the  rock  is  stated  in  table  2.  It  is  the  most  silicic  of  the 
andesitic  group  of  rocks  from  Lassen  Peak.  It  has  a  lower  water  content  than  any 
rock  other  than  quartz  basalt  which  has  been  analyzed  from  that  field,  with  the 
exception  of  its  own  vesicular  modification.  The  water  was  determined  by  the 
Penfield  method,  and  was  checked  by  a  more  elaborate  method  (exhaustion  of  the 
water  on  heating  the  powder  in  vacuo ,  with  subsequent  absorption  by  P205). 
Fhe  results  were  in  the  closest  accord.  The  ferric  ratio  1  is  0.281,  and  the  gas- 
content  is  10.6  c.  c.  per  gram,  at  1200°  C.  (see  p.  48).  Volatile  constituents  seem 
to  be  present  in  the  Lassen  rocks  in  amounts  not  determinable  with  certainty  by 
gravimetric  methods.  Cl  and  S  were  determined  in  this  rock,  on  large  portions, 
blank  determinations  being  made  at  the  same  time.  The  results  merely  prove  the 
presence  of  these  constituents  but  can  not  be  accepted  as  an  accurate  measure  of 
the  amounts  present.  The  results  of  gas  analysis,  given  below,  afford  a  much  more 
reliable  appraisal. 

The  petrological  study  of  this  rock,  then,  shows  it  to  resemble  the  rocks  of  which 
the  crater  region  of  Lassen  Peak  is  built.  Chemically  it  resembles  certain  dacitic 
rocks,  which  have  been  analyzed,  from  the  northwest  base  of  the  mountain.2 
As  a  volcanic  product  it  represents  material  which  is  in  anything  but  a  state  of 
equilibrium,  judging  from  the  condition  of  the  biotite,  the  nature  of  the  plagioclase 
phenocrysts,  and  the  variable  composition  of  the  glass.  Physically  also  it  has 
suffered  a  great  amount  of  shattering  and  movement.  It  is  just  the  kind  of  mass 
which  would  be  expected  from  an  old  conduit  lining  and  plug,  slowly  forced  upward 
after  being  shattered  and  locally  heated  by  ascending  gases  or  otherwise. 

fhe  second  modification  of  the  new  lava  is  a  pumiceous  or  vesicular  andesite, 
much  lighter  in  color  than  the  dense,  glassy  variety.  It  apparently  forms  the 
interior  portions  of  the  blocks  on  the  cracked  and  fissured,  crusted  and  expanded 
surface  of  the  new  lava  filling  the  crater.  Its  vesicular  character,  and  consequent 
lighter  color,  and  its  rough,  hackly  fracture,  distinguish  it  from  the  dense  andesite. 
In  places  the  vesicles  show  a  rough  alignment  due  to  movement  of  the  mass.  Micro¬ 
scopically  it  resembles  the  dense  form  very  closely,  and  has  not  been  given  such 
detailed  optical  study.  The  glass  is  lighter  and  more  uniform  in  color,  and  less 
variable  in  index  than  is  the  dense  variety.  The  chemical  composition  of  this  rock 
is  stated  in  table  2.  It  parallels  that  of  the  dense  variety  closely,  though  it  is 
slightly  more  silicic.  It  is  lower  in  water  content  than  any  rock  from  the  Lassen 
region  (excluding  the  quartz  basalts)  which  has  been  analyzed.  Its  ferric  ratio  is 
0.362,  and  the  gas  content  7.8  c.  c.  per  gram  at  1200°  C.  Thus  there  is  more  ferric 
iron  and  less  gas  than  in  the  dense  variety. 

1  The  ferric  ratio  is  the  ratio  of  Fe203  in  the  rock  to  the  total  amount  of  iron  in  the  rock  reckoned  as  Fe203.  It  will  be 
used  here  as  a  thermal  index. 

2  A.  Hague  and  J.  P.  Iddings,  Notes  on  the  volcanoes  of  Northern  California,  Oregon,  and  Washington  Territories,  Am. 
Journ.  Sci.  (3),  25,  222-235,  1 883 .  U.  S.  Geol.  Surv.  Bull.  591,  169-175,  1915. 


45 


The  third  modification  is  a  dense,  gray,  glassy  outer  layer  found  upon  some 
blocks,  both  dense  and  pumiceous.  We  refer  to  it  as  the  bread-crust  variety. 
It  is  usually  about  3  cm.  in  thickness  and  merges  gradually  into  the  normal  dense  or 
pumiceous  form.  As  it  is  obviously  the  same  material  as  the  latter  a  complete 
analysis  was  not  made.  The  biotite  calls  for  comment.  A  flake  5  mm.  from  the 
outer  surface  of  a  specimen  of  the  bread-crust  variety  was  decidedly  biaxial,  with 
7  greater  than  1.67.  Within  the  vesicular  portion  of  the  specimen,  about  30  cm. 
from  the  surface,  a  flake  showed  7  =  1.67.  The  glass  of  the  bread-crust  is  decidedly 
clearer  and  lighter  in  color  than  that  of  the  dense  variety.  It  is  not  vesiculated, 
however.  The  ferric  ratio  of  this  variety  is  0.480,  and  the  gas  content  9.5  c.  c.  per 
gram  at  1200°  C.  The  bread-crust  variety  seems  to  have  had  the  most  drastic 
natural  reheating.  Its  ratio  and  gas  content  are  higher  than  those  of  the  pumiceous 
variety,  and  suggest  that  it  has  been  affected  by  rising  gases  under  oxidizing  con¬ 
ditions. 

WATER  CONTENT  OF  CONDUIT  LAVA. 

It  has  been  stated  above  that  the  conduit  lava  is  strikingly  low  in  water 
content.  This  applies  to  all  three  modifications  and  has  been  verified  in  several 
ways.  With  the  exception  of  the  quartz  basalts,  the  Lassen  volcanic  rocks  are  all 
significantly  richer  in  water  than  the  new  lava.  The  various  water  determinations 
are  stated  below.  Those  from  the  rock  analyses  were  carried  out  by  the  Penfield 
method;  only  one  check  by  the  P206  method  was  made  (p.  44);  the  values  from 
the  gas  analyses,  determined  upon  150  grams  of  rock,  which  was  broken  into  lumps, 
and  hence  free  from  the  plus  error  due  to  adsorption  of  water  shown  by  powders, 
are  produced  here,  calculated  to  weight  per  cent. 


Rock. 

On  rock  powders. 

Rock  fragments — 
gas  analysis. 

Penfield  method. 

P2O5  method. 

Dense  andesite . 

0.35 

n.d. 

0.150 

Pumiceous  andesite . 

0.18 

0.183 

0.113 

Bread-crust  andesite . 

n.d. 

n.d. 

0.133 

It  is  evident  that  the  bread-crust  variety  contains  more  water  than  the 
pumiceous,  both  being  lower  in  water  than  the  dense  andesite.  Results  to  date  show 
that  a  similar  relation  holds  true  between  bread-crust  and  pumice  from  Martinique. 
The  bread-crust  contains  considerably  more  water  than  the  corresponding  andesitic 
pumice.  This  general  poverty  in  water  content  in  comparison  with  other  rocks  of 
the  Lassen  region  is  appropriate  evidence  in  support  of  the  hypothesis  that  the 
lava  which  was  pushed  up  to  fill  the  crater  is  an  old  rock  which  has  been  reheated. 
The  higher  water  content  of  the  bread-crust  surface  may  be  due  to  surface 
exposure  to  H20  (gas)  at  high  temperature  and  pressure  (see  pp.  76  and  following). 


46 


GAS  CONTENT  OF  CONDUIT  LAVA.1 

The  gas  content  of  rocks  has  been  investigated  by  various  students,  and  the 
previous  work  well  summed  up  by  Chamberlin  in  his  “Gases  in  Rocks.”  Unfor¬ 
tunately  none  of  these  investigators  has  given  any  special  attention  to  the  relation 
between  the  composition  of  the  rock  and  the  gases  obtained  from  it.  Nor  has  any 
one  of  them  except  Gautier  remembered  that  H20  is  a  regular,  and  perhaps  the 
most  important,  constituent  to  be  determined.  The  gas  content  of  the  material  of 
the  1915  eruption  of  Lassen  Peak  was  examined  in  connection  with  a  general  study 
of  this  problem  of  the  gases  in  the  rocks  which  is  now  in  progress.  The  results 
are  tabulated  in  table  3. 2  About  150  grams  of  rock,  preferably  obtained  from  the 
interior  of  a  specimen,  in  order  to  avoid  accidental  contamination,  were  placed  in  a 
silica  tube  which  had  been  heated  and  exhausted  of  its  own  gases  before  the  speci¬ 
men  was  introduced. 

Table  3. 

(Volume  percentage  composition  of  total  gases.  Andesite,  Lassen  Peak  eruption  of  1915.  Basalt  from  Kilauea.) 


Dense. 

Pumiceous. 

Bread-crust. 

Aa. 

Pahoehoe. 

CO, . 

1  .959 

1 .187 

2.071 

6.80 

5.673 

CO . 

0.503 

0.310 

0.623 

3.83 

0.601 

II . 

1 .187 

0.210 

0.412 

6.18 

1 .085 

n2 . 

0.029 

0.116 

0.577 

1 .31 

0.269 

A . 

0.0003 

0.018 

0.003 

0.01 

0.003 

SO, . 

n.  d. 

n.d. 

0.009 

0.26 

0  .  404 

S, . 

0.123 

0.215 

0.882 

n .  d . 

1 .384 

CL . 

0.129 

0.428 

0.297 

0.26 

0  .404 

F, . 

n.d. 

n.d. 

1 .524 

n.d. 

n.d. 

11,0 . 

96.067 

97.519 

93.658 

80.17 

90.580 

Total  gases  per  gram  of 
rock,  at  760  mm.  and 
1200°  C . 

10 .6  c.c. 

7.8  c.c. 

9 .5  c.c. 

9.8  c.c. 

5  .4  c.c. 

The  first  feature  to  attract  attention  was  the  obvious  presence  of  considerable 
amounts  of  fluorine.  This  showed  itself  by  etching  the  glass  tubes  next  to  the 
furnace.  Unfortunately,  in  only  one  analysis  was  a  reasonable  attempt  at  its 
determination  possible.  In  the  absence  of  data  on  other  rocks  too  much  emphasis 
must  not  be  laid  upon  this  fluorine  content,  which  may  be  due  in  part  to  the  biotite. 
One  has  the  impression,  however,  that  the  amount  is  much  too  great  to  be  accounted 
for  in  this  way  alone. 

In  general,  the  volume  of  gas  per  gram  of  rock  is  the  first  matter  of  interest. 
If  these  quantities  be  calculated  on  a  weight  per  cent  basis  they  are  insignificantly 
small,  but  expressed  by  volume  at  760  mm.  and  1200°  C.  (the  temperature  at  which 

1  With  the  co-operation  of  E.  S.  Shepherd. 

2  Table  3  gives  the  volume  percentages  of  gases  obtained  by  heating  the  rock  in  vacuo  to  about  1200°  C.  It  must  be 
remembered  that  carrying  out  computations  to  the  third  or  fourth  decimal  place  is  not  evidence  of  great  precision  in  the 
analytical  work,  but  a  result  of  including  in  the  computation  about  0.2  gm.  H,0  which  is  weighed  as  such.  Similarly  the 
halogens  and  sulphur  (except  SO2)  have  to  be  determined  gravimetrically  and  included  in  the  computation.  In  general, 
the  fixed  gases  amount  to  about  10  c.  c.,  which  are  passed  over  into  the  apparatus  and  analyzed.  When  computed  to  760  mm. 
and  1200°  C.,  the  water  vapor  usually  amounts  to  about  a  liter,  so  that  the  other  constituents,  if  they  are  to  be  expressed 
at  all,  must  be  given  in  decimals. 


47 


all  the  volatile  constituents  of  the  rock  would  exist  as  gases),  they  may  be  used, 
together  with  the  rock  analysis,  in  any  discussion  of  the  composition  of  the  material. 
In  the  case  of  the  new  lava  of  Lassen  Peak  it  will  be  noted  that  the  dense  andesite 
and  the  bread-crust  variety  show  about  the  same  gas  content,  while  the  pumiceous 
portion  has  lost  an  appreciable  amount  of  its  gas.  The  relation  is  similar  to  that 
of  the  Hawaiian  lava  given  in  table  3  for  comparison.  The  halogens  run  higher  in 
the  pumiceous  and  bread-crust  varieties,  that  is,  in  the  modifications  supposedly 
most  subjected  to  reheating  in  the  conduit.  Hydrogen  seems  to  be  definitely  higher 
in  the  original,  dense  andesite,  and,  in  a  general  way,  it  might  be  said  that  the  sup¬ 
posed  reheating  has  been  accompanied  by  some  slight  oxidation  of  the  volatile 
matter.  A  similar  relation  seems  to  exist  in  the  gases  of  the  Hawaiian  lavas. 

It  was  most  astonishing  to  find  fluorine  ranking  with  C02  as  a  major  volatile 
constituent.1  While  it  would  be  unwise  to  infer  too  much  from  this  one  measure¬ 
ment,  apparently  the  fluorine  content  was  high  in  the  other  two  varieties  also. 
Mr.  Perret,  in  his  volcano  studies  in  the  Mediterranean  region,  has  noted  that  the 
initial  stages  of  an  eruption  are  usually  characterized  by  predominant  halogens, 
whereas  the  declining  stages  show  sulphur  compounds  predominant.2  This  observa¬ 
tion  is  in  accord  with  what  we  have  so  far  observed.  At  Kilauea,  where  the 
halogens  are  minimal,  it  was  found  in  the  1912  gas  collections,  which  involved  about 
1,000  liters  of  gas,  that  fluorine  was  about  twice  as  abundant  as  chlorine,  while  at 
Mount  Katmai,  Alaska,  it  was  found  to  be  only  about  one-fourth  as  abundant. 
Of  course,  in  ordinary  field  observations  a  distinction  between  fluorine  and  chlorine 
is  not  feasible,  and  it  is  possible  that  fluorine  has  frequently  been  overlooked.  It 
combines  so  readily,  and  its  compounds  are  so  easily  obscured  or  removed,  that  it 
may  prove  to  have  been  present  in  many  places  without  attracting  the  attention 
which  it  merits. 

It  is  within  the  bounds  of  probability  that  fluorine  will  prove  to  be  not  only  a 
significant  factor  in  the  mineralogical  composition  of  the  plutonic  rocks,  but  also 
that  its  presence  or  absence  may  give  some  hint  as  to  the  nature  and  past  history  of 
petrogenic  processes.  For  the  present  it  will  suffice  to  note  that  the  renewal  of 
volcanic  activity  at  Lassen  Peak  was  accompanied  by  an  appreciable  quantity 
of  this  elusive  element.  The  actual  amount  of  gases  present  in  these  rocks  after 
they  have  reached  the  surface  is  of  course  not  great  in  weight  per  cent;  on  the  other 
hand,  the  volume  of  gas  which  these  rocks  can  yield  when  heated  is  significant.  In 
the  above  analyses  it  appears  that  there  is  still  available,  for  each  kilo  of  rock,  some 
10  or  more  liters  of  gas  (total  volatile  matter,  including  water).  Presumably  this 
is  only  a  small  portion  of  the  gas  content  of  these  lavas  when  below  the  surface. 

1  Since  the  above  was  written  a  similar  high  fluorine  content  has  been  observed  in  the  gases  from  the  Martinique  lavas. 

2  The  observations  are  in  general  accord  with  those  of  Sainte-Claire  Deville  at  Etna  (1857)  and  elsewhere,  Fouque  at 
Santorini  (1865),  and  other  observers.  For  the  literature  see:  F.  W.  Clarke,  The  data  of  geochemistry,  U.  S.  Geol.  Surv., 
Bull.  695,  255-284,  1920;  and  F.  von  Wolff,  Der  Volkanismus,  635,  1914. 


48 


FERRIC  RATIO  IN  CONDUIT  LAVA.1 

Determinations  of  FeO,  Fe203,  and  Si02  were  made  on  the  three  varieties  of 
the  andesite,  before  and  after  treatment  for  the  extraction  of  the  gases.  The  results 
are  shown  in  table  4.  Si02  was  determined  (to  the  first  place  of  decimals)  in  order 
to  ascertain  if  the  fused  rock  made  any  appreciable  attack  upon  the  silica  tube, 
which  it  evidently  does  not,  and  also  as  a  test  of  the  unilormity  of  the  samples. 
The  iron  values  are  taken  from  the  rock  analyses  for  the  dense  variety.  For  the 
other  samples  the  determinations  were  made  on  special  portions  by  the  method  of 
decomposition  with  hydrofluoric  acid.  The  samples  varied,  as  might  be  expected, 
within  narrow  limits.  In  order  that  the  values  might  be  compared  directly,  the 
figures  from  the  actual  determinations  have  been  recalculated  on  the  basis  of  an 
average  value  of  4.82  per  cent  of  total  iron  expressed  as  Fe203.  The  ferric  ratio,  of 
course,  is  not  affected  by  the  recalculation. 


Table  4. — Ferric  Ratio  in  the  Conduit  Lava,  Lassen  Peak,  1915. 


Treatment. 

Si02 

Fe203 

FeO 

Total  Fe 
as  Fe2Os 

Ferric 

ratio. 

Dense,  glassy  andesite. 

(1)  None . 

63.2 

1 .30 

3  .00 

4.63 

0.281 

(2)  780°  C.  for  5  hours  in  steam  and  C02 . 

62.7 

1 .57 

2  .70 

4.57 

0.343 

(3)  1260°  C.  for  3  hours  in  vacuo . 

63.4 

1.73 

2  .90 

4.95 

0.349 

Pumiceous  andesite. 

(4)  None . 

64.2 

1  .75 

2  .77 

4.83 

0  362 

(5)  1260°  C.  for  4  hours  in  vacuo . 

63.3 

1 .79 

2.75 

4.85 

0.369 

Bread-crust  surface  of  pumiceous  andesite. 

(6)  None . ' . 

64.1 

2  .34 

2  .28 

4.87 

0.480 

(7)  1260°  C.  for  4  hours  in  vacuo . 

64.2 

1 .78 

2.73 

4.82 

0.369 

Recalculated  values,  assuming  an  average  of  4.82  per 

cent  Fe 

AS  Fe2Oj 

(1)  None . 

63.7 

1 .35 

3.12 

4.82 

0.281 

(2)  780°  C.  for  5  hours  in  steam  and  CO> . 

63.7 

1  .65 

2.85 

4.82 

0.343 

(3)  1260°  C.  for  3  hours  in  vacuo . 

63  .7 

1  .68 

2.83 

4.82 

0.349 

(4)  None . 

63.7 

1 .75 

2.76 

4.82 

0.362 

(5)  1260°  C.  for  4  hours  in  vacuo . 

63.7 

1 .78 

2.73 

4.82 

0.369 

(6)  None . 

63.7 

2.32 

2.25 

4.82 

0.480 

(7)  1260°  C.  for  4  hours  in  vacuo . 

63.7 

1 .78 

2.73 

4.82 

0.369 

Summary  statement  of  the  Changes  in  the  Ferric  Ratio. 


Rock  variety. 

Untreated. 

780°  C.  in  steam 
and  C02. 

1260°  C.  in  vacuo. 

Gas-content  in 
c.  c./gm.  at 

1200°  C. 

Dense . 

0.281 

0.343  (5  hrs.) 

0  .349  (3  hrs.) 

10.6 

Pumiceous . 

0.362 

0.369  (4  hrs.) 
0.369  (4  hrs.) 

7.8 

9.5 

Bread-crust . 

0.480 

In  recalculating  the  average  values  (2)  was  excluded,  being  a  small  sample, 
unduly  rich  in  phenocrysts  and  poor  in  glass.  The  values  obtained  from  the 
determinations  on  (2)  were,  however,  raised  to  the  average  value,  on  the  assumption 
that  the  relations  of  FeO  and  Fe203  would  be  the  same  as  in  the  other  samples. 


1  With  the  co-operation  of  M.  Aurousseau. 


49 


For  this  particular  material  the  ratio,  as  stated  above,  suggests  the  attainment 
of  equilibrium  after  the  rock  has  been  heated  for  some  hours  in  a  neutral  atmosphere, 
or  in  vacuo.  The  results  obtained  are  in  accord  with  the  other  evidence  in  showing 
that,  of  the  three  varieties  of  material,  the  dense  andesite  has  suffered  least  in  the 
natural  process  of  reheating.  1  reated  in  the  laboratory  its  ferric  ratio  approaches 
that  of  the  pumiceous  variety,  which  itself  is  but  little  affected  by  laboratory 
treatment. 

THERMAL  STUDY  OF  CONDUIT  LAVA  A 
MINERAL  CHANGES  ON  HEATING. 

Biotite  and  glass  are  the  constituents  of  the  rock  most  sensitive  to  thermal 
treatment.  The  first  studies  were  confined  to  the  stability  of  biotite  when  heated 
through  a  range  of  temperature,  both  in  air  and  in  a  neutral  atmosphere.  Heated  in 
air  a  biotite  from  granite  (7  =  1 .64)  began  to  lose  weight  at  500°  C.,  even  in  an  hour’s 
time.  At  650°  C.  it  had  become  reddish  and  decidedly  biaxial,  with  7=  1.69.  This 
decomposition  occurs  in  two  ways;  one  is  by  loss  of  volatile  matter,  the  other  by 
oxidation.  The  oxidation  is  the  chief  factor  in  the  development  of  biaxiality,  red¬ 
dening,  and  the  increase  of  7.  The  biotite  of  the  dense  andesite,  as  stated  above, 
also  showed  decided  reddening  with  a  high  value  for  7;  that  of  the  bread-crusted 
variety  shows  the  same  characters  but  in  a  decreasing  degree  from  the  outer  surface 
of  the  crust  inward. 

In  a  neutral  atmosphere 1  2  biotite  persists  fairly  well  at  850°  C.  but  shows 
increasing  decomposition  with  further  rise  in  temperature.  Above  900°  C.  there  is 
fairly  rapid  decomposition  with  the  formation  of  magnetite.  The  clearing  of  the 
glass  proceeds  with  increased  rapidity  as  the  temperature  rises  above  850°  C.  Thus, 
15  minutes  at  1050°  C.  yields  a  clear,  nearly  colorless  glass.  Changes  in  the 
biotite  and  glass  are  indicated  in  the  experiments  detailed  in  the  following  section. 
Plagioclase  and  pyroxene  are  but  little  affected  at  these  temperatures  during  such 
short  periods  of  exposure,  though  material  subjected  to  a  higher  temperature  shows 
a  little  less  pyroxene. 

In  the  dense,  glassy  andesite  the  biotite  always  shows  partial  decomposition, 
with  the  formation  of  reaction  rims,  and  on  reheating  to  temperatures  above  840°  C. 
it  decomposes  with  increasing  rapidity,  even  in  the  short  exposures  here  employed. 
Unless,  therefore,  the  effect  of  pressure  upon  the  stability  of  biotite  is  considerable, 
it  seems  reasonable  to  suppose  that  this  lava  could  not  have  been  heated  above 
850°  C.  at  anytime  after  it  approached  the  surface;  otherwise,  in  the  large  blocks, 
which  would  have  remained  hot  for  some  time  after  reaching  the  surface,  a  complete 
breakdown  of  the  biotite  would  be  expected.  From  the  condition  of  the  biotite, 
and  the  phenomenon  of  glass-clearing,  we  may  reasonably  infer  that  we  are  here 
dealing  with  a  relatively  low-temperature  eruption  so  far  as  surface  phenomena  are 
concerned. 

1  With  the  co-operation  of  E.  S.  Shepherd  and  H.  E.  Merwin. 

2  Eor  rocks  and  minerals  relatively  low  in  ferrous  iron  this  atmosphere  was  provided  by  steam  and  C02  obtained  by 
passing  a  slow  current  of  C02  through  boiling  distilled  water  and  passing  the  mixture  over  red-hot  copper  before  it  came  in 
eontact  with  the  minerals  (or  rocks),  which  are  placed  in  a  silica  tube. 


50 


BENDING  (FLOW)  TEMPERATURE  OF  DENSE  ANDESITE. 

For  the  purposes  of  this  study,  small  prisms  were  cut  Irom  the  dense  andesite 
and  were  heated  for  varying  lengths  of  time  in  the  neutral  atmosphere  mentioned 
above.  Such  prisms  of  dimensions  of  about  5  X  10  X  50  mm.  were  supported  at  first 
at  both  ends  and  allowed  to  sag  in  the  middle;  in  later  experiments  they  were  sup¬ 
ported  by  one  end  and  at  an  angle  of  about  450  in  order  to  get  a  somewhat  sharper 
indication  of  softening. 

(a)  Below  yoo°  C. — Very  little  change  occurs  in  the  time  available  for  a  laboratory  experi¬ 

ment. 

(b)  770°  to  j8o°  C.  for  5  hours. — No  change  was  noted,  even  on  a  polished  surface  of  the 

prism. 

(c)  840°  C.  for  3  hours. — A  polished  surface  showed  minute  warping  and  the  glass,  which 

was  originally  brownish,  had  become  much  clearer. 

{d)  030°  to  gpo°  C.  for  il4  hours. — A  prism  50  mm.  long,  supported  at  one  end,  had  bent 
about  io°,  swelled  appreciably  owing  to  the  beginning  of  vesiculation,  and  the 
glass  was  perfectly  clear  and  colorless.  The  biotite  was  unoxidized,  but  the  time 
interval  was  short  and  the  biotite  was  completely  inclosed  in  the  glass. 


Fig.  28. — A  prism  of  dense  Lassen  andesite,  supported  at  two  points  and  heated  to  1040°  C. 

for  1  5  minutes.  Note  the  sag  at  ends  and  center.  Photo  Snapp. 

(e)  1040°  C.  for  13  minutes. — A  prism  supported  at  both  ends  sagged,  swelled,  and  developed 
a  glazed  surface  (see  fig.  28).  The  glass  was  colorless  in  thicknesses  which,  in 
the  original,  were  decidedly  brownish. 

(/)  io5°°  t0  II00°  C.  for  42  hours,  closing  with  several  hours  at  the  lower  temperature. — The 

glass  formed  is  clear,  except  as  stained  by  the  dissolving  biotite,  all  of  which  has 
decomposed,  leaving  spicules  of  magnetite  and  brownish  streamers  of  color. 
No  evidence  of  recrystalhzation  was  observed. 

(g)  1260°  C.  for  4  hours. — Shows  only  solution  effects.  The  glass  is  brownish,  with  rela¬ 
tively  few  crystals  embedded  in  it.  The  index  of  refraction  of  the  glass  reached 
1.530.  The  feldspar  phenocrysts,  while  reduced  in  size  and  corroded,  were  not 
fused  and,  if  anything,  were  more  shattered  than  before. 

Such  results  obtained  from  the  thermal  study  of  biotite  will  eventually  be  of 
general  application  when  the  series  of  minerals  known  as  biotite  has  been  more 
thoroughly  investigated  and  the  thermal  behavior  correlated  with  composition,  etc. 
It  must  be  emphasized,  however,  that  the  behavior  of  the  dense  glassy  andesite  from 
Lassen  Peak,  as  studied  here,  is  peculiar  to  that  particular  rock.  No  inference 
can  yet  be  made,  from  its  behavior,  concerning  the  behavior  of  other  andesites,  even 


51 


if  chemically  resembling  it.  For  example,  the  andesites,  dacites,  and  pumices  of 
Mont  Pelee,  Martinique,  are  now  being  studied  in  the  same  way.  They  bear 
a  general  resemblance  to  the  Lassen  Peak  rocks,  but  their  behavior  on  thermal 
treatment  is  quite  different.  Whereas  the  dense  andesite  from  Lassen  begins 
to  soften  at  about  850°  €.,  a  similar  rock  from  Mont  Pelee  does  not  do  so  until 
about  1200°  C.  A  glassy  basalt  from  Kilauea  crystallizes  on  reheating  after 
which  it  does  not  again  soften  at  the  low  temperature  at  which  it  first  flowed  from 
the  crater  (from  noo°  C.  down  to  6oo°  C\);  furthermore,  the  gas  content  of  the 
Lassen  rock  can  hardly  be  accepted  as  typical  of  the  gas  content  of  similar  andesites 
in  general. 

GENERAL  EFFECTS  OF  HEATING  TO  1260°  C. 

All  three  modifications  of  the  rock,  when  heated  in  vacuo  for  3  or  4  hours,  in 
order  to  pump  off  the  gases,  yield  identical  products.  The  mass  becomes  vesi- 
culated  and  the  crystals  of  the  ground-mass  go  into  solution,  though  the  phenocrysts 
do  not  do  so  noticeably.  The  glass  reaches  an  index  of  1.530  rather  uniformly. 
It  is  brownish  in  color,  with  relatively  few  crystals  embedded  in  it.  The  biotite 
disappears  completely.  The  ferric  ratio  of  the  product  tends  to  approach  the 
value  0.369,  strongly  suggestive  of  the  attainment  of  a  condition  of  equilibrium. 
The  actual  values  for  the  ferric  ratio  after  this  treatment  are: 


Variety. 

Value  for 
ferric  ratio. 

Hours 

heating. 

Dense,  glassy  variety . 

0.349 

3 

Pumiceous  variety . 

0.369 

4 

Bread-crust  variety . 

0.369 

4 

It  is  to  be  noted  that  the  ferric  ratio  of  the  pumiceous  variety  was  0.362 
before  treatment  in  this  way,  and  we  may  infer  that  it  has  already  had,  in  nature,  a 
thermal  treatment  comparable  with  that  given  it  in  the  laboratory.  The  ratio  for 
the  dense  variety  has  increased  on  treatment,  the  time  of  heating  being  less  than 
with  the  others,  while  that  of  the  bread-crust  has  actually  decreased.  The  last, 
being  a  surface  modification,  would  have  been  subject  to  oxidizing  conditions  in 
nature,  while  the  pumiceous  interior  of  the  same  blocks  would  be  relatively  pro¬ 
tected.  We  conclude  that  the  three  modifications  represent  the  same  original  mate¬ 
rial,  each  having  been  subjected  to  its  own  peculiar  conditions  of  thermal  alteration. 

SOME  CONCLUSIONS  FROM  LABORATORY  STUDIES  OF  THE  CONDUIT  LAVA. 

The  lava  extruded  during  the  1915  eruption  of  Lassen  Peak  is  an  andesitic  or 
dacitic  rock.  It  is  variably  brecciated,  and  the  glass  of  the  ground-mass  is  variable 
in  amount  and  composition  within  narrow  limits  and  over  short  distances. 

The  plagioclase  phenocrysts  show  several  periods  of  alternating  resorption  and 
growth,  with  concurrent  shattering.  The  larger  pyroxenes  have  been  shattered 
and  the  biotite  has  begun  to  decompose.  These  features  indicate  repeated  reheat- 


52 


ing  and  cooling  under  differential  stresses  without  the  attainment  of  thermal  equili¬ 
brium.  The  greater  basicity  of  the  feldspar  of  the  ground-mass  and  the  vanishing 
quartz  indicate  changes  in  composition  other  than  those  due  to  gradually  falling 
temperature  in  a  melt  having  the  composition  of  this  rock  as  a  whole. 

Specimens  of  this  lava  heated  under  suitable  laboratory  conditions  give  a  gen¬ 
eral  idea  of  the  temperatures  which  may  have  operated  at  the  surface  during  the 
doming-up  of  the  massive  conduit  lava.  Under  laboratory  conditions  850°  C. 
seems  the  lowest  temperature  at  which  the  material  could  be  deformed  without 
considerable  fracturing.  On  the  other  hand,  the  biotite  in  cracks  in  the  surface 
rock  and  the  unvesiculated  character  and  opacity  of  the  glass  indicate  a  prevailing 
temperature  lower  than  this. 

It  should  be  remembered  also  that  the  material  tested  in  the  laboratory  had 
presumably  lost  the  major  portion  of  the  volatile  matter,  which  exerts  a  consider¬ 
able  influence  on  the  viscosity  of  lavas,  from  which  it  is  proper  to  infer  that  the 
figures  obtained  in  the  laboratory  represent  maximum  temperatures,  and  that  the 
actual  temperatures,  if  they  differed  from  these,  would  have  been  lower  rather  than 
higher. 

This  lava  of  1915  does  not  seem  to  have  been  a  new  magma  erupted  through 
an  old  conduit.  It  seems  rather  more  like  an  old  conduit  lining,  which  had  been 
fissured  and  reheated  by  a  fresh  influx  of  juvenile  gases  from  below  until  finally 
it  acquired  sufficient  mobility  to  allow  it  to  be  forced  upward  by  pressure.  The 
eruption  of  both  pumiceous  and  dense  lava  together  favors  this  hypothesis  of 
irregular  reheating  along  cracks  in  part  of  the  old  conduit  lining. 

Whatever  the  source  of  energy,  the  mass  ultimately  acquired  a  sufficient 
fluidity  to  permit  it  to  reach  the  surface,  where  some  of  it  was  too  cold  to  expand 
into  pumiceous  form,  while  the  more  highly  heated  portions  continued  to  expand 
and  contributed  to  the  enormous  amount  of  ash  which  spread  over  the  surrounding 
country.  It  seems  probable  that  the  upward  movement  of  the  crater  plug  may 
have  been  an  abortive  attempt  at  spine  formation,  but  the  power  behind  it  was 
released  prematurely  through  a  weak  spot  in  the  eastern  crater  wall. 

It  appears  therefore  to  be  a  clear  conclusion  from  the  mineral  content  and 
physical  relations  within  the  conduit  lava,  which  alone  afford  a  proximate  clue  to 
conditions  within  the  volcano,  that  the  eruption  was  in  singular  measure  a  low- 
temperature  phenomenon. 

“A  careful  re-examination  of  this  mass  of  ‘dense  glassy  andesite’  and  associated 
material  in  May  1923  shows  that  rock  of  this  type  is  exposed  over  an  area  of  only 
a  few  hundred  square  meters.  It  is  split  vertically  into  large,  often  monolithic, 
blocks  with  the  rifts  decidedly  widened  at  the  top.  These  rifts  are  smooth  fractures 
except  near  the  bottom  of  a  few  of  them,  where  the  surfaces  are  rough  for  a  vertical 
distance  of  a  meter  or  so  upward  from  the  lowest  point  accessible,  as  though  formed 
by  the  pulling  apart  of  a  pasty  mass.  This  (lowest)  portion  of  the  block  is  slightly 
vesiculated  and  the  glass  cleared  to  some  extent  but  not  reddened. 

“In  the  western  notch  this  dense  rock  gradually  gives  place  to  a  coarse  breccia 
of  red  dacite,  similar  to  the  top  of  Lassen  Peak,  in  a  matrix  of  red,  vesiculated 


53 


andesite.  This  material  (the  westerly  two-thirds  of  the  crater  mass)  is  a  jumble  of 
broken  blocks  which  individually  show  flow  textures,  though  they  are  not  oriented 
in  any  particular  direction.  On  the  other  hand,  the  mass  which  forms  the  northeast 
corner  of  the  crater  is  composed  of  large,  shattered,  monolithic  blocks  of  glassy 
andesite  which  have  obviously  been  pushed  up  along  the  old  crater  wall.  It  is 
significant  that  these  blocks  did  not  bend  over  and  their  sides  are  not  warped 
appreciably,  even  where  they  overhang.  Some  of  the  horizontal  cracks  (2  to  10  cm. 
wide)  between  such  blocks  were  found  filled  with  ash,  loose  fragments  of  old 
dacite,  and  even  thin  plates  of  glassy  andesite,  the  whole  scarcely  at  all  compacted. 
There  were  no  fingers  of  lava  between  the  fragments  filling  these  cracks.  One  thin 
plate  of  glassy  andesite  was  bent  but  was  not  vesiculated  nor  had  the  glass  cleared. 
Certainly  none  could  have  been  very  hot. 

“No  evidence  was  found  to  support  any  interpretation  of  the  phenomenon  as  a 
lava  flow,1  at  least  not  in  the  usual  sense  of  that  expression.  It  has  neither  top, 
bottom,  nor  sides,  while  the  material  of  the  western  end  is  appreciably  less  inti¬ 
mately  related  than  that  near  the  source,  though  grading  irregularly  into  it.  If, 
however,  we  accept  the  hypothesis  that  the  1915  upheaval  merely  brought  up  the 
old  plug  or  conduit  lining,  all  of  the  observed  facts  fit  together  without  difficulty.” 
(Memorandum  by  E.  S.  Shepherd,  1923.) 


1  Cf.  Professor  Holway,  p.  18. 


CHAPTER  III. 

FIELD  EVIDENCE  OE  TEMPERATURE  RELATIONS. 

HORIZONTAL  BLASTS. 

It  would  be  a  matter  of  very  great  interest  and  of  no  little  importance  in  inter¬ 
preting  the  mechanism  of  the  eruption  to  fix  the  temperature  of  the  two  horizontal 
blasts  of  May  19  and  22,  but  as  there  were  no  eyewitnesses,  so  also  no  thermometer 
was  available  to  record  the  temperature  attained.  It  is  significant  that  except  in  one 
small  area  no  fire  was  started  by  the  blasts,  although  on  all  sides  the  foliage  of  the 
standing  evergreens  was  found  scorched  and  brown.  Around  the  blasted  area  both 
standing  trees  and  smaller  undergrowth  seemed  completely  dead,  but  as  the  summer 
advanced  it  appeared  that  they  were  not  so,  and  most  of  these  trees  attained  to 
complete  restoration  of  their  foliage  before  the  following  winter.  Both  leaves  and 
branches  were  somewhat  blackened  at  the  most  exposed  points,  but  nowhere  was  the 
appearance  as  if  the  branches  themselves  were  burning  and  so  contributing  to  the 
heat.  Rather  they  appeared  to  be  scorched  or  singed,  as  though  by  momentary 
exposure  to  heat  which  either  was  not  sufficiently  high  or  was  of  too  short  duration 
to  set  the  trees  on  fire. 

On  the  borders  of  the  devastated  zone  small  trees  and  bushes  which  were 
partly  embedded  in  snow  suffered  no  damage  below  the  snow  line  from  the  passing 
blasts.  The  exposed  portion  above  the  snow  was  either  carried  away  or  completely 
blasted,  indicating  more  definitely  high  velocity  and  high  temperature.  Toward 
the  center  of  the  area  everything  was  carried  away  root  and  branch  and  no  trace  of 
snow  or  of  vegetation  remained. 

The  single  area  in  which  fire  was  started  was  a  steep  hillside  forming  a  part  of 
the  boundary  of  the  Lost  Creek  basin,  exactly  facing  the  mountain  at  a  distance  of 
about  3.5  miles  and  a  little  to  the  north  of  the  axis  of  greatest  intensity  of  the  blast. 
(See  Sketch  Map,  fig.  29.)  The  second  blast  (May  22)  must  have  struck  against 
the  broadside  of  this  steep  hill  and  have  been  so  far  checked  in  its  progress  that  the 
vegetation  upon  the  hillside  endured  a  considerably  longer  exposure  to  its  heat  than 
in  those  areas  over  which  it  merely  passed  by.  Elsewhere  the  momentary  passage 
of  the  blast  was  wholly  insufficient  to  kindle  dead  leaves,  splinters,  and  small  twigs, 
but  on  this  opposing  hillside  these  were  set  on  fire  and  somewhat  charred.  Both 
the  extent  and  intensity  of  the  fire  appear  to  have  been  small,  which  is  explained  in 
part  by  Eorest  Ranger  Seaborn,  who  reports  that  the  fire  was  soon  quenched  by 
rainfall  (probably  condensation  from  the  steam  cloud).  It  is  also  possible  that  the 
second  blast  was  considerably  hotter  than  the  first,  but,  finding  no  inflammable 
material  left  in  the  track  of  the  earlier  blast,  no  fire  was  kindled  except  at  this  com¬ 
paratively  remote  point.  To  judge  by  the  appearance  of  this  hillside  3  or  4  weeks 
afterward,  the  fire  must  have  been  altogether  insignificant,  for  the  depth  of  penetra¬ 
tion  into  the  dead  leaves  which  lined  the  hillside  was  small  and  dead  leaves  on  the 

54 


55 


pine  trees  were  only  charred  at  their  outer  extremities,  the  fire  being  insufficient  even 
to  burn  up  all  of  the  exposed  dead  foliage  (fig.  30). 

Of  course,  the  effect  of  such  a  hot  blast  depends  upon  two  factors,  the  temper¬ 
ature  and  the  time  of  exposure.  If  the  time  of  exposure  were  extremely  short  the 
temperature  might  be  very  high  and  still  cause  no  fire.  On  the  other  hand,  an  ex¬ 
posure  of  even  2  or  3  minutes  to  a  much  lower  temperature  might  kindle  such 


SO  At 


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Fig.  29. — April  28,  1922.  Sketch  Map  showing  a  portion  of  Lassen  Volcanic  National 
Park.  Devastated  area  shown  in  black.  2  miles  =  I  inch  (approximately). 
(Courtesy  of  Mr.  M.  E.  Dittmar,  Secretary,  Lassen  Volcanic  National  Park 
Association.) 

vegetation  immediately.  In  a  crude  laboratory  test  it  appeared  that  about  i6o°  C. 
for  one  minute  would  blast  pine  foliage  in  the  same  manner  as  the  foliage  was 
blasted  along  the  boundaries  of  Lost  Creek,  but  a  higher  temperature  (and  a  shorter 
time  of  exposure)  may  have  prevailed  during  the  period  of  destruction  there  and 
still  fall  far  short  of  the  temperatures  appropriate  to  red  heat  in  the  crater  (6oo° 
minimum).  It  also  happened  that  the  portion  of  the  devastated  zone  nearest  to 


56 


the  source  of  the  blast  was  also  the  most  barren,  so  that  immediately  adjacent  to  the 
mountain  the  temperature  of  the  blast  might  have  been  as  high  as  300°  or  400°  C. 
without  finding  material  upon  which  such  a  temperature  could  have  left  evidences  of 
burning.  In  the  center  of  the  track  of  the  explosion  no  snow  was  found  by  Loomis 
and  his  party,  who  visited  it  before  the  second  blast  on  May  22.  On  the  adjacent 
hillside  the  snow  was  more  or  less  protected  by  a  cover  of  rocks  and  small  stones, 
projected  by  the  earlier  explosions,  which  blanketed  the  regions  to  the  north  and 
south  of  the  devastated  zone  to  a  depth  varying  from  2  feet  down  to  a  few  inches. 
These  stones  nowhere  melted  their  way  through  the  snow  and  so  could  not  have  been 
hot  at  the  time  when  they  alighted.  Even  on  the  summit  the  explosions  had 
covered  the  snow  surrounding  the  explosion  crater  to  the  depth  of  several  feet  with 
rocks  and  ash  without  melting  it,  except  in  the  case  of  a  few  very  large  boulders 
weighing  several  tons,  which  penetrated  through  the  snow  (fig.  31).  Their  mo- 


charred  at  base  of  Jessen  Mt.  on  Lost  Creek, 
May  22,  1915,  by  a  hot  blast  from  Lassen 
Peak.  Photo  Diller. 


mentum  must  have  accomplished  most  of  this  result,  for  they  appear  to  have  had 
no  excess  heat  through  which  to  melt  any  considerable  body  of  the  surrounding 
snow.  The  solid  ejectamenta,  therefore,  contributed  little  of  the  heat  which  melted 
away  the  snow.  Ihis  observation  also  is  of  some  importance  in  considering  the 
extent  to  which  hot  magma  became  exposed  during  this  eruption. 

It  appears  from  the  evidence  bearing  upon  the  temperature  of  the  blast,  as 
observed  upon  the  snow  and  vegetation  remaining  along  the  borders  of  the  zone  of 
destruction,  that  we  must  abandon  any  thought  of  extremely  high  temperature  or 
else  assume  that  the  velocity  of  the  blast,  even  upon  its  outskirts,  was  still  so  great  as 
to  prevent  combustion. 


57 


As  we  approach  the  source  of  the  horizontal  outburst  just  below  the  upheaved 
lava  “  lid  "  at  the  summit,  we  have  to  consider  the  situation  from  a  different  view¬ 
point.  No  momentary  blast,  however  hot,  can  be  assumed  to  have  carried  away 
such  an  accumulation  of  snow  as  existed  in  the  bay  of  the  mountain  itself  by  melting 


Fig.  31. — June  28,  1915.  Bread-crusted  boulder  im¬ 
bedded  in  the  snow  on  the  summit  showing 
that  the  boulder  was  cold  when  it  fell.  Note 
also  smaller  rocks  and  debris  lying  on  the 
snow.  Photo  Day. 

from  the  top  downward,  for  we  know  that  under  normal  exposure  to  the  sun  an 
entire  summer  does  not  suffice  to  do  this.  Either  the  snow  was  cleared  away 
mechanically  by  a  very  low-angle  blast  of  extreme  velocity,  which  conclusion  finds 
support  in  the  fact  that  the  whole  valley  was  swept  clear  of  vegetation,  root  and 


58 


branch,  as  well  as  the  snow;  or  near  the  mountain  there  must  have  been  continued 
or  repeated  outpourings  of  hot  vapors  of  lower  intensity  but  of  reasonably  long 
duration.  There  is  some  little  difficulty  with  either  assumption  considered  alone. 
A  downward  blast  of  extreme  violence  might  carry  away  the  snow,  even  though  it 
were  a  hundred  feet  deep,  but  if  so  this  snow  must  have  been  scattered  rather  than 
melted,  and  so  would  have  caused  no  such  flood.  If,  on  the  other  hand,  a  con¬ 
siderable  outpouring  of  hot  gases  at  low  velocity  be  assumed,  the  flood  is  accounted 
for,  but  not  the  destruction  to  the  trees. 

There  must  have  been  at  least  one  blast  of  sufficient  intensity  to  carry  out  all 
the  vegetation  in  the  valley  for  a  distance  of  4  miles,  and  in  addition  to  this  the 
accumulated  snow  on  the  mountain  slope  near  the  source  of  the  blast  must  have 
received  sufficient  heat  to  melt  it  completely,  except  for  the  comparatively  small 
residue  of  ice  remaining  in  the  photograph  (fig.  11).  That  the  destructive  horizon¬ 
tal  blast  was  of  extremely  high  temperature  or  of  long  duration  seems  impossible, 
for  the  reason  that  at  its  borders  there  is  no  evidence  of  fire  (with  the  single  excep¬ 
tion  above  noted).  To  account  for  the  great  body  of  snow  melted,  some  supple¬ 
mentary  agency  must  therefore  be  sought.  Either  the  great  horizontal  blast  was 
followed  by  hot  gas  exhalations  of  low  velocity  for  several  hours  thereafter,  or,  as 
seems  to  the  authors  much  more  probable,  the  condensation  of  superheated  steam 
from  the  volcano  cloud,  which  certainly  did  continue  for  several  hours,  falling  on  the 
snow  to  leeward  of  the  mountain,  furnished  the  major  portion  of  the  heat  which 
melted  the  snow  and  caused  the  floods.  The  fact  that  both  of  the  great  floods 
(the  night  of  May  19  and  the  afternoon  of  May  22)  appeared  to  leeward  of  the 
mountain  accords  with  this  view.  The  further  fact  that  a  flood  occurred  on  May 
22  at  all,  after  all  the  snow  had  been  carried  out  on  the  19th,  probably  admits  of 
no  other  explanation  than  this. 

The  heavy  body  of  ash  contributed  materially  to  the  immense  quantity  of 
solid  matter  which  the  first  flood  carried  down,1  but  not  to  the  heat  of  melting.  It 
seems  most  probable,  therefore,  that  the  first  violent  blast  blew  down  most  of  the 
trees  in  Lost  Creek  Valley  and  the  flood  of  hot  ash-laden  rain,  mingled  with 
the  snow,  carried  the  trunks  within  its  reach,  together  with  the  boulders,  out  of  the 
valley  along  the  line  of  Lost  Creek  and  Hat  Creek  and  stranded  them  among  the 
standing  timber  below.  The  fact  that  they  were  carried  around  a  sharp  bend  to 
the  northward,  about  3  miles  from  the  explosion  center,  indicates  this  mode  of 
transportation.  The  large  boulders,  both  those  remaining  in  the  crater  and  those 
detached  by  the  explosion  and  sent  down  the  mountain  to  be  distributed  by  the 
flood  waters,  were  ol  andesite  and  were  readily  identified  as  a  part  of  the  original 
summit  cone,  though  some  of  them  were  moved  for  a  distance  as  great  as  4  miles 
(see  photograph,  fig.  13).  These  boulders  were  not  new  lava,  nor  were  any  of  them 
of  a  temperature  higher  than  the  probable  temperature  of  the  flood  which  bore 
them  to  their  present  resting-place,  as  may  be  seen  from  the  fact  that  wood  in 
contact  with  them  was  not  blackened.  Several  of  these  boulders  weighed  many 
tons  each  (fig.  14). 

1  Forest  Ranger  Seaborn  reported  that  a  bucket  filled  from  the  flood  and  allowed  to  stand  over  night  showed  only  ioper 
cent  in  depth  of  clear  water  in  the  morning,  indicating  a  very  large  content  of  solid  matter. 


59 


LAVA  TEMPERATURE  AND  “FLOW.” 

It  has  already  been  pointed  out  that  few  or  no  experienced  observers  of  volcanic 
phenomena  were  witnesses  of  either  of  the  two  great  eruptions.  It  is  therefore 
necessary  to  build  a  somewhat  hypothetical  structure  out  of  the  actual  observations 
of  individuals  with  little  experience  in  such  matters,  and  such  studies  as  could  be 
made  on  the  ground  and  in  the  laboratory  after  the  eruptions  had  ceased. 

In  making  such  a  composite  analysis  Mr.  Milford’s  direct  observation  (p.  16) 
is  of  importance.  From  the  statements  of  his  party,  which  included  a  number  of 
people,  it  is  perfectly  clear  that  red-hot  material  appeared  at  the  surface  on  the 
night  of  May  19,  probably  for  the  first  and  last  time  during  this  eruptive  cycle. 
The  report  says  explicitly  that  both  the  lava  and  the  glow  were  “deep-red”  or 
“vivid-red,”  which  probably  fixes  a  temperature  between  6oo°  and  75 o°  (see  pp. 
49,  et  seq.).  The  report  further  says  that  at  intervals  of  8  or  10  minutes  molten 
material  flowed  out  of  the  western  notch  in  the  crater  rim  like  slag  out  of  a  crucible, 
but  observations  on  the  ground  show  no  evidence  of  recent  fluidity,  and  laboratory 
studies  show  that  the  rock  is  solid  and  not  liquid  at  those  temperatures,  so  that  this 
particular  conclusion  must  be  modified.  Under  high  pressure  in  a  closed  chamber 
with  a  considerable  percentage  of  water  still  in  solution,  the  magma  might  con¬ 
ceivably  be  somewhat  mobile  at  750°,  but  immediately  the  pressure  is  relieved  at  the 
surface  the  excess  of  water  will  escape  and  the  residual  silicate  become  immediately 
rigid.  Boulders,  some  of  them  probably  red-hot,  did  break  off  at  the  point 
observed  and  rolled  down  the  mountain  in  the  direction  indicated.  It  would  there¬ 
fore  seem  more  likely  that  the  material  which  reached  the  surface  was  solid 
throughout  all  of  the  events  observed.  The  Milford  party,  after  all,  was  21  miles 
away.  Lassen  andesite  would  require  to  have  a  temperature  above  900°  to  flow 
under  its  own  weight  in  the  open  air,  unless  ejected  by  force  in  the  form  of  an  emul¬ 
sion,  and  above  1250°  to  “splash”  in  the  manner  indicated  in  Mr.  Milford’s  descrip¬ 
tion.  Such  a  flow  (at  1250°)  would  be  white-hot  and  of  blazing  brilliancy,  and  not 
deep-red,  as  the  Milford  party  saw  it.  Moreover,  it  would  contain  no  biotite; 
indeed,  all  the  crystals  of  the  ground-mass  would  be  converted  into  glass.  On  the 
other  hand,  the  breaking  away  of  boulders  from  a  solid  mass  at  a  temperature 
between  6oo°  and  750°  (red  heat)  certainly  would  lay  bare  fresh  bright-red  surfaces. 
Presumably  one  of  these  surfaces  belonged  to  the  rock  which  rolled  down  the  moun¬ 
tain,  while  the  place  from  which  it  broke  away  remained  behind  and  slowly  cooled 
to  blackness.  Flashes  of  this  kind,  some  moving  and  some  still,  appear  to  offer  a 
rational  explanation  of  what  the  Milford  party  witnessed.  This  accords  well  with 
the  observed  red  heat  and  with  the  present  formation  of  the  mass  on  this  (west) 
side  of  the  mountain  (fig.  10). 

After  the  summit  crater  had  been  filled  (figs.  26,  32,  33)  by  the  eruptions  of  May 
19  and  22,  the  exposed  rocks  over  much  of  the  upheaved  area  (the  volcano  plug)  are 
uniformly  reported  by  observers  (Flowed,  Spaulding,  Yori)  to  have  been  hot. 
Heated  air  rose  from  the  cracks  and  the  radiation  from  the  surface  appears  to  have 
been  uncomfortable  enough  to  prevent  the  Spaulding  party  from  venturing  out 
upon  the  debris  which  filled  the  crater,  but  when  the  writer  visited  the  summit, 


60 


3  weeks  later,  no  such  limitation  was  experienced;  it  was  quite  possible  to  walk 
without  discomfort  over  any  portion  of  the  newly  upheaved  mass.  Some  of  these 
rocks,  particularly  the  largest  boulders,  on  the  southern  margin  of  the  plug,  were 
too  hot  for  the  unprotected  hand  when  pressed  against  them  and  held  there,  but 
were  not  otherwise  uncomfortable.  The  northern  half  of  the  plug  was  cold  or 
nearly  so.  In  one  crack  on  the  south  side  a  thermometer  thrust  into  the  ash  to  the 
depth  of  a  foot  showed  a  temperature  of  150°  immediately,  and  no  doubt  would  have 
gone  somewhat  higher  but  for  the  limitations  of  the  thermometer.  A  week  later 
a  temperature  of  250°  was  measured  by  Shepherd  in  a  similar  crack.  No  evidence 
of  combustion  was  found  upon  the  summit  nor  was  any  smell  of  sulphur  or  other  of 
the  usual  volcano  gases  found  there,  except  for  a  faint  trace  of  hydrochloric  acid, 


Fig.  32. — July  26,  1913.  View  in  the  Summit  Crater  of  Lassen  Peak  after  the  upheaval 
(on  or  about  May  19,  1915).  Photo  Loomis. 


barely  detectable  in  one  or  two  places.  Against  this,  however,  it  should  be  borne 
in  mind  that  Spaulding’s  party,  one  week  after  the  great  explosion,  reports  odors  of 
sulphur  and  strongly  acid  gases  at  the  summit.  But  when  one  recalls  that  strongly 
acid  fumes,  when  judged  only  by  the  effect  upon  breathing,  probably  indicate  a 
concentration  no  greater  than  0.5  per  cent  by  volume  with  air,  and  this  at  the 
source  itself,  the  quantity  of  acid  gases  given  off  must  have  been  insignificant,  even 
during  the  period  of  maximum  activity. 

These  observations  bring  into  the  foreground  a  point  which  has  been  considered 
already  (pp.  52,  53)  but  which  is  the  subject  of  some  difference  of  opinion.  The 
newly  erupted  material  on  the  west  side  of  the  mountain  extends  beyond  the 
old  rim  of  the  crater  about  1,000  feet,  ending  in  a  narrow  point.  Diller  has  de¬ 
scribed  this  as  a  lava  stream  flowing  through  the  notch  in  the  crater  rim.  He  says 


61 


(private  letter  Oct.  3,  1922):  “It  is  my  opinion  that  the  lava  erupted  from  Lassen 
Peak,  May  19,  1915,  really  formed  a  lava  stream,  broken  to  solid  fragments  on  the 
surface  of  the  flow,  but  stiffly  viscous,  slowly  flowing  beneath,  thus  enabling  it  to 
move  down  the  slope  gently  from  the  overflowing  top  of  the  volcanic  vent  over  the 
bed  of  the  old  crater  lakelet,  whose  drainage  it  followed  to  the  rim  of  the  old  crater, 
where  it  broke  over  the  steep  western  slope,  forming  the  wonderful  spectacle  seen 
by  Mr.  Milford/’  It  is  probable  that  he  found  support  for  this  view  in  Milford’s 
observations  discussed  above.  He  has  not  called  attention  to  features  of  the  flow 
itself  which  point  to  this  conclusion,  beyond  comparing  its  general  appearance  with 
the  nearby  flow  of  Cinder  Cone,  which,  however,  is  a  quartz  basalt  and  presumably 


Photo  Day. 

more  fluid  than  Lassen  dacite  or  andesite.  Its  silica  content  is  given  as  56  per  cent 
compared  with  68  per  cent  for  the  dacite  (p.  37).  There  is  also  abundant  evidence 
of  high  temperature  at  Cinder  Cone  which  is  not  found  at  Lassen  Peak.  Perhaps 
it  should  be  emphasized,  in  view  of  the  fact  that  a  surface  flow  has  been  explicitly 
insisted  upon  by  a  geologist  of  such  long  experience,  that  a  careful  examination  of 
the  new  lava  on  the  west  side  of  the  mountain  does  not  reveal  surface  evidence  of 
recent  flow.  Neither  do  the  deep,  gaping  crevices  yield  indications  of  fluidity  near 
the  surface.  In  appearance  it  suggests  nothing  but  boulders  and  debris,  (see  fig. 
33).  A  highly  viscous  lava,  such  as  this,  if  sufficiently  hot  and  flowing  to  its  present 
position  en  masse,  would  rather  have  advanced  in  great  rounded  lobes  like  heavy 


62 


sirup  filling  a  spoon  or  like  the  acid  lavas  of  Lipari.  Nothing  of  this  formation  is 
suggested  here.  Lassen  dacite  is  in  fact  solid  at  red  heat  and  not  liquid,  but  suppos¬ 
ing  it  to  have  been  above  red  heat  and  fluid  enough  to  move  through  the  notch  under 
the  action  of  gravity,  it  is  difficult  to  see  how  a  flow  could  possibly  have  taken  the 
present  form. 

A  supposition  that  the  lava  upheaval  was  really  much  hotter  than  the  surface 
evidence  has  indicated  has  been  offered  by  Diller  (personal  communication)  in 
support  of  his  belief  that  the  spur  on  the  western  slope  is  a  true  liquid  flow  and  in¬ 
deed  is  indispensable  to  such  a  conclusion.  The  supposition,  however,  encounters  a 
number  of  difficulties  already  pointed  out  as  follows: 

1.  The  lava  in  the  western  notch  was  found  to  be  cold  when  we  visited  it,  4  weeks  after 
the  eruption,  at  the  time  when  the  eastern  portion  was  still  hot,  as  noted  above.  It  there¬ 
fore  appears  not  to  have  been  one  of  the  hotter  portions  of  the  upheaved  area,  which  could 
be  assumed  to  be  more  mobile  because  superheated. 

2.  The  words  of  Professor  R.  S.  Holwav,  of  the  University  of  California,  an  expe¬ 
rienced  observer  (quoted  on  page  18),  who  visited  the  crater  only  5  days  after  the  upheaval 
occurred,  are  important  in  this  connection:  “Nor  were  there  found  any  rocks,  old  or  fresh, 
bearing  evidence  of  recent  fusion.”  E.  S.  Shepherd  has  reached  the  same  conclusion 

(P-  53)- 

3.  The  single  assured  case  of  viscous  conduit  lava  in  situ ,  offered  by  Diller  in  support 
of  his  contention  (Plate  6,  No.  2),  was  not  found  in  the  western  notch,  but  at  the  opposite 
end  of  the  crater.  It  is,  in  fact,  located  at  the  summit  of  a  steeper  slope  (fig  35)  than  the 
western  notch  and  much  nearer  the  center  of  activity,  nevertheless  it  shows  no  tendency 
to  flow  from  its  point  of  emergence  down  the  slope. 

4.  Unaltered  biotite  is  found  everywhere  in  Mount  Lassen  andesite  (dacite).  In  the 
laboratory  this  biotite  becomes  biaxial  and  suffers  partial  dehydration  when  exposed  to 
the  air  at  650°;  when  exposed  in  an  atmosphere  of  steam  and  air  it  begins  to  show  oxida¬ 
tion  and  turns  reddish  brown  a  few  degrees  above  8oo°  (cf.  p.  49).  At  neither  of  these 
temperatures  is  dacite  fluid  enough  to  move  under  its  own  weight.  If  dacite  actually 
emerged  into  the  air  at  a  temperature  above  8oo°  the  biotite  would  certainly  be  quickly 
altered.  Nothing  of  this  has  been  found  on  the  dacite  surfaces  thus  far  studied.1 

5.  At  the  point  where  Diller  has  indicated  that  the  lava  “broke  over  the  rim”  there 
has  been  a  considerable  settling  of  the  new  lava  since  the  upheaval  in  1915.  The  general 
contour  of  the  surface  was  then  convex  to  an  observer  looking  down  upon  it  from  either 
side  (north  or  south).  It  is  now  distinctly  concave,  as  may  be  seen  from  figure  34,  the  con¬ 
cavity  extending  entirely  across  the  western  notch.  There  are  of  course  no  bench  marks 
through  which  to  attempt  a  measurement  of  this  depression,  but  it  may  be  estimated  at 
from  25  to  30  feet.  Whether  this  settling  has  significance  here  or  not  may  be  a  matter  of 
opinion,  but  to  us  it  has  seemed  more  probable  that  the  solid  surface  of  a  viscous  plug 
might,  after  upheaval,  settle  more  easily  than  a  stream-flow  over  an  old  and  cold  bench. 

It  therefore  appears  from  field  studies,  no  less  than  from  the  laboratory  studies  already 
cited,  that  this  exposed  tongue  of  lava  was  moved  to  its  present  position  after  solidification 
of  its  surface,  not  before.  It  could  not  have  flowed  through  the  notch  to  its  present  posi¬ 
tion  under  any  conditions  of  which  we  have  any  present  indication.2 

If  this  spur  of  lava  did  not  reach  its  present  position  by  flow  it  must  have  been 
pushed  up  from  below  along  with  the  rest  of  the  volcano  “plug,”  and  this  assump- 


1  Except  in  the  bread-crust  bombs,  page  71. 


2  See  also  p.  51  et  seq. 


PLATE  6 


(1)  A  part  of  the  exposed  eastern  end  of  the  volcano  plug. 

(2)  An  instance  of  flow  structure  in  situ  cited  by  Diller  (p.  62). 

(3)  (Center)  A  large  block  from  the  original  plug  (solid)  tilted  outward  90°  by  the 

upheaval.  Photo  Day. 


M  imm 
Of  THt 


URRflMrr  m  n. 


63 


tion  seems  to  accord  well  with  the  form  of  the  spur  and  with  the  east-and-west 
faulting  of  the  crater,  concerning  which  other  evidence  has  been  adduced. 

For  example,  supervisor  Rushing,  of  the  Forest  Service,  writes  to  Professor 
Holway  under  date  of  September  30,  1914  (before  the  upheaval)  as  follows:  “The 
crater  has  opened  up  on  the  west  side  of  the  mountain  for  a  considerable  distance 
and  considerable  quantities  of  steam  issue  from  its  entire  length.”  (p.  12).  Again 
in  a  letter  to  J.  S.  Diller,  December  14,  he  says:  “The  crater  on  the  west  side  near 
the  top  is  much  enlarged  and  the  entire  west  slope  of  the  mountain  is  discolored  by 
volcanic  dust.”  (p.  13).’  W.  H.  Spaulding  in  the  (unpublished)  memorandum  of 


Fig.  34. — August  14,  1923.  Looking  west  across  the  upheaved  area  eight  years  later. 

Note  the  concave  sky-line.  (cf.  fig.  26)  Photo  Day. 


his  visit  to  the  mountain  on  May  30  (after  the  upheaval)  has  offered  a  similar  view; 
he  says  of  this  western  spur:  “It  appeared  that  the  mountain  had  been  cleft  and 
that  a  tremendous  fissure  extended  down  into  the  mountain  about  1,000  feet.  The 
whole  west  half  of  the  mountain  appeared  shattered.”  Finally,  Loomis  and  Miss 
Dines  reported  (pp.  14,  15)  that  the  western  notch  was  already  filled  by  a  black 
mass  thrust  up  into  it  before  May  19. 

There  is  also  evidence  that  the  east  rim  of  the  bowl  was  similarly  broken 
through  by  the  same  upheaval,  furnishing  some  of  the  great  blocks  which  were 
subsequently  carried  down  Lost  Creek  Valley  with  the  flood.  The  form  of  the  up- 
heaved  mass  from  east  to  west  is  also  such  as  would  be  given  to  a  volcano  plug, 
solid  above  but  viscous  below,  rising  in  an  open  funnel. 


1  See  also  accurate  description  by  Olsen  following  a  personal  visit  on  Oct.  io,  1914.  Appendix  p.  178. 


64 


On  the  eastern  slope,  a  little  to  the  south  of  Diller’s  viscous  extrusion  (Plate  6, 
No.  2),  there  is  also  to  be  found  a  great  lava  block  from  the  easternmost  end  of  the 
plug,  which  has  been  tilted  outward  90°  from  the  position  in  which  it  originally 
solidified,  as  may  be  plainly  seen  from  its  structure  (Plate  6,  No.  3).  Outward  tilt¬ 
ing  is  rather  to  be  expected  when  a  shattered  plug  emerges  at  the  funnel  rim.  Both 
the  eastern  and  western  notches  gave  opportunity  for  such  outward  tilting,  and  evi¬ 
dences  of  it  are  abundant. 

The  total  area  of  the  upheaved  portion  of  the  summit  is  about  2,000  feet  in 
length  by  about  800  feet  in  width  in  the  widest  part.  The  western  end  is  sharply 
pointed,  while  the  eastern  end  is  truncated,  perhaps  by  breaking  off  over  the  steep 
precipice  which  forms  the  eastern  rim,  but  more  likely  by  the  emergence  of  the 
horizontal  blast  at  this  point.  These  fragments  were  carried  several  miles  by  the 
flood.  The  general  form  of  the  upheaved  area  is  that  of  the  explosion  crater  which 
it  fills,  plus  the  additions  east  and  west  along  the  fault  and  tapering  out  toward 
the  west  end.  Being  generally  convex  upward,  it  is  deeply  cleft  at  several  points 
where  it  was  broken  up  during  the  operation  of  upheaval  in  an  open  funnel.  In 
short,  it  has  the  usual  appearance  of  a  volcanic  plug,  without  complicating  features, 
shoved  upward  300  feet  or  more,  after  which  the  motive  power  appears  to  have 
found  release  at  the  side  rather  than  through  the  top  in  the  fearful  explosions  of 
May  19  and  22.  There  is  no  record  of  any  upward  movement  of  the  mass  after 
the  latter  date.  The  appearance  of  the  upheaved  region  is  well  shown  by  photo¬ 
graphs  (figs.  26,  32,  33). 

MECHANICS  OF  UPHEAVAL  OF  PLUG  AND  OF  HORIZONTAL  BLASTS. 

It  is  desirable  to  endeavor  to  correct  a  misunderstanding  which  appears  to 
have  arisen  regarding  the  present  appearance  of  the  upheaved  structure  and  of 
the  rocks  freshly  exposed  thereby.  Rock  fragments  showing  inclusions  and 
local  flow  structures  in  nowise  establish  the  fact  that  these  inclusions  were  acquired, 
or  that  any  of  this  flow  structure  was  formed  during  the  present  eruption.  A  vol¬ 
canic  plug,  from  its  very  nature,  must  be  made  up  of  these  features  and  little  else. 
These  should  be  clearly  distinguished,  however,  from  flow  structure  in  situ,  of  which 
Messrs.  Diller  and  Paige  were  fortunate  enough  to  find  an  isolated  case  (Plate  6,  No.  2), 
just  beyond  the  northeast  end  of  the  upheaved  area.  Other  observers,  so  far 
as  known,  have  found  flow  structure  only  in  fragments  now  entirely  disconnected 
from  the  parent  magma,  that  is  to  say,  in  material  which  obviously  came  to  its 
present  position  after  complete  solidification. 

In  view  of  the  temperature  of  the  upheaved  material,  and  the  fact  that  it  was 
simply  elevated  300  feet  or  thereabouts,  while  retaining  undisturbed  its  continuous 
connection  with  the  magma  below,  it  is  probable  that  there  is  a  continuous  and 
fairly  rapid  increase  in  temperature  downward  in  this  upheaved  mass.  Attention 
has  already  been  called  to  a  dust-filled  surface  crack  in  which,  5  weeks  after  the 
great  eruption,  a  thermometer  indicated  250°  C.  Volcanic  dust  is  a  very  poor 
conductor  of  heat,  so  that  this  temperature,  persisting  very  near  the  surface  for 
weeks  after  the  eruption  occurred,  may  very  well  confirm  the  observation  of  red 


65 


heat  during  the  eruption,  and  the  inference  of  a  steep  temperature  gradient  down¬ 
ward.  It  is  of  course  a  matter  of  accident  along  this  gradient  whether  300  feet  of 
elevation  would  be  sufficient  to  expose  any  viscous  material  or  not.  That  viscous 
material  was  there,  immediately  below  the  solid  plug,  appears  to  be  unquestioned  by 
anyone.  The  top  of  the  plug,  however,  stopped  in  its  movement  about  at  the  level 
of  the  crater  rim  and  so  very  little  opportunity  was  given  for  the  appearance,  still 
less  for  the  outpouring,  of  the  viscous  material  which  pushed  it  up.  The  exposure 
at  the  northeast  end,  where  the  steep  slope,  aided  by  the  explosions,  broke  off  the 
easternmost  portion  of  the  rim  and  exposed  the  plug,  is  therefore  probably  the  only 
tangible  evidence  of  its  structure  below  the  surface  which  will  be  found. 

There  is  some  danger  of  confusing  an  otherwise  clear  picture  with  a  multitude 
of  details,  some  of  which  find  different  interpretations  in  the  hands  of  different 
observers,  and  so  do  not  strengthen  the  picture  at  all.  To  us  the  features  of  lava 
movement  found  in  the  western  notch  are  not  to  be  appraised  as  an  expression  of 
viscous  flow  during  this  eruption,  but  as  most  excellent  evidence  of  the  east-and- 
west  faulting  of  the  summit  crater,  which  afforded  relief  to  the  excess  pressure  within 
the  mountain,  and  perhaps  prevented  its  demolition,  (1)  by  “loosening”  the  plug, 
and  (2)  through  the  release  of  confined  gases  (mainly  steam)  in  horizontal  blasts 
from  beneath  the  plug  at  the  east  end.  Something  of  this  was  seen  at  Martinique 
in  1902,  but  elsewhere  mechanisms  of  this  kind  are  relatively  rare.  The  viscous 
extrusion  in  situ  observed  by  Paige  and  Diller  may  be  of  value  as  evidence  that 
viscous  lava  did  actually  reach  the  surface  during  this  eruption,  but  the  strength  of 
the  evidence  is  somewhat  impaired  by  the  fact  that  it  appears  to  bear  no  obvious 
relation  to  the  present  activity.  That  it  came  to  its  present  position  through 
viscous  flow  is  unquestioned,  but  if,  after  examining  Plate  6,  No.  2,  we  shift  our  view¬ 
point  somewhat  in  order  to  bring  this  extrusion  into  perspective  with  the  crater  rim, 
it  will  be  found  outside  the  hot  zone  of  present  activity.  There  is  also  undistorted 
lava  exposed  between  this  extrusion  and  the  present  center  of  activity,  as  may  be 
seen  from  figure  35.  This  feature  loses  some  of  its  significance,  therefore,  from  its 
outlying  position.  It  may  very  well  be  a  product  of  some  earlier  eruption  rather 
than  of  this  one.  On  the  other  hand,  it  does  strengthen  our  picture  of  the  mechan¬ 
ism  of  the  upheaval  to  find  evidences  of  viscosity  at  the  deepest  point  within  the 
plug  which  came  to  be  exposed  during  this  eruption  (fig.  35,  foreground). 

It  will  be  recalled  that  the  horizontal  blast  to  the  eastward  really  came  out  from 
beneath  the  “lid”  because  the  containing  vessel  (the  rim)  yielded  at  this  point. 
The  explosion  which  released  the  pressure  beneath  carried  away  200  feet  or  more  of 
the  thinnest  portion  of  the  rim,  and  the  lava  plug  is  therefore  exposed  in  vertical 
section  in  this  area  alone.  This  vertical  section  (roughly  triangular,  about  200  feet 
wide  and  75  feet  deep,  see  fig.  11)  of  the  east  end  of  the  plug  appears  not  to  have 
been  examined  by  earlier  observers  because  of  its  inaccessibility,  but  during  the 
summer  of  1923  a  special  effort  was  made  to  reach  the  bottom  of  it.  This  effort 
was  rewarded  with  evidences  of  viscous  flow  at  the  point  where,  in  the  opinion  of  the 
writers,  it  is  most  important  to  find  it.  Figure  35  (foreground)  will  permit  one  to 


66 


see,  as  well  as  the  unfortunate  afternoon  light  permitted,  the  curved  contours  at 
the  base  of  the  portion  of  the  plug  now  exposed. 

It  may  be  of  interest  to  advance  a  further  hypothesis  which  may  account  in 
part  for  the  shattered  condition  of  the  surface  of  the  plug.  All  of  the  explosions 
previous  to  May  19  were  out  of  the  main  crater  and  generally  vertical,  except  in  so 
far  as  they  were  influenced  by  the  direction  of  the  wind.  On  May  19  there  was  a 
horizontal  blast  from  a  different  point  and  on  the  22d  another,  both  of  terrific 
violence,  as  is  shown  by  the  uprooting  and  laying  down  of  all  the  forest  trees  for  a 
distance  of  more  than  4  miles  in  the  direction  taken  by  the  blast. 


Fig.  35. —  Another  view  looking  northwest  across  the  exposed  eastern  end  of  the  volcano 
plug.  At  the  top  of  the  picture  (right)  may  be  seen  Mr.  Diller’s  example  of  flow 
in  situ  (Cf.  Plate  6,  2).  Just  to  the  left  of  it  and  projecting  up  between  it  and 
the  crater  (adjacent  notch)  is  a  similar  outcrop  of  undeformed  lava.  In  the 
foreground  viscous  movement  is  indicated  in  several  places.  Photo  Day. 

The  upheaval  above  noted  probably  began  just  before  May  19.  The  point  of 
greatest  weakness  in  the.  inclosing  cone  was  on  its  northeast  side,  where  but  a  very 
thin  wall  inclosed  the  plug,  the  outside  slope  being  extremely  steep  at  this  point 
and  probably  faulted.  Also,  the  apparent  center  of  the  most  violent  explosive 
activity  preceding  the  upheaval  at  the  summit  is  near  this  side  of  the  crater  bowl. 


67 


It  would  therefore  seem  possible  to  infer  that  the  upheaval  of  the  old  plug  was  tanta¬ 
mount  to  lifting  the  “lid/'  from  beneath  which  the  two  side  explosions  then  took 
place  by  tearing  away  some  200  feet  of  the  shell  of  the  old  crater  bowl  which  was 
thinnest  at  that  point.  The  violence  ot  these  explosions  was  sufficient  to  shake  up 
and  break  up  the  lid  without  being  quite  sufficient  to  blow  it  off  the  mountain.  It 
may  be  likened  to  a  train  of  dynamite  which  is  laid  for  the  purpose  of  blasting  out  a 
roadway.  The  explosions  are  not  planned  to  be  sufficiently  violent  to  blow  the 
rocks  completely  out  of  the  roadway,  but  only  to  break  them  up  so  as  to  facilitate 
their  subsequent  removal.  The  rocks  forming  the  present  surface  of  the  volcanic 
plug  appear  to  have  been  loosened  in  some  such  manner  as  this,  while  the  maximum 
violence  of  the  explosion  developed  sidewise  from  underneath  the  lid  at  the  point 
which  proved  weakest.  Viewing  this  side  of  the  mountain  from  the  valley  below, 
a  point  can  be  clearly  seen  (fig.  n)  which  may  very  well  have  been  the  source  of 
this  blast.  It  lies  just  at  the  bottom  of  the  exposed  section  of  the  “lid,”  with  a 
fault  extending  downward  from  it.  This  intersection  of  the  lid  with  the  rift  in  the 
mountainside  probably  indicates  the  locus  of  greatest  structural  weakness.  Also, 
when  this  point  was  first  seen  by  the  authors,  some  4  weeks  after  the  explosion, 
steam  was  still  issuing  from  the  rift  for  several  yards  below  the  lid,  and  in  May  1916 
these  fumaroles  could  still  be  seen. 

There  is  some  reason  for  believing  that  the  horizontal  blast  of  the  afternoon  of 
May  22  did  not  follow  absolutely  the  same  direction  as  that  of  the  19th.  The 
trees  laid  down  by  the  first  blast  were  in  the  central  floor  and  the  southern  slope  of 
Lost  Creek  Valley.  The  trees  on  the  northern  slope  of  the  valley  were  still  standing 
after  this  blast,  but  not  after  that  of  May  22.  Both  groups  of  trees  lie  with  their 
trunks  pointing  directly  away  from  the  same  point  in  the  mountain,  namely,  the 
exposed  end  of  the  lid.  It  would  appear,  therefore,  that  both  blasts  emerged  from 
the  same  point,  but  the  second  took  a  slightly  more  northerly  course  than  the  first. 

Also,  we  may  not  overlook  the  fact  that  on  both  the  occasions  when  these 
blasts  were  directed  down  Lost  Creek  Valley  there  were  terrific  vertical  explosions 
also;  whether  at  the  same  moment,  or  shortly  before  or  after,  may  not  be  known, 
for  there  was  no  witness  of  either  of  the  two  horizontal  blasts.  Neither  are  there 
any  photographs  of  the  vertical  blast  of  May  19,  which  occurred  in  the  night. 
The  vertical  blast  of  May  22  was  photographed  from  all  directions  over  the  entire 
countryside,  the  volcano  cloud  being  one  of  the  most  magnificent  spectacles  which 
it  is  ever  the  fortune  of  students  of  volcanoes  to  observe.  It  ascended  to  a  height 
of  about  25,000  feet  above  the  summit  in  volutes  of  the  heavy  cauliflower  type  in  an 
otherwise  clear  sky.  Although  very  spectacular  in  appearance,  the  violence  of 
these  explosions  was  not  sufficient  to  modify  the  form  of  the  volcano  or  to  dislodge 
any  considerable  portion  of  its  structure.  Unlike  the  great  eruption  of  Vesuvius 
in  1906,  when  the  crater  rim  was  lowered  several  hundred  feet,  and  the  eruption  of 
Katmai  in  Alaska  in  1912,  when  the  shape  of  the  cone  was  radically  altered  by  the 
scattering  of  a  cubic  mile  or  more  of  the  summit  crater  and  its  contents,  these  two 
explosions  merely  served  to  shake  up  the  top  of  the  plug  and  to  tear  away  a  section  of 
the  thin  eastern  rim,  scattering  boulders  and  smaller  fragments  about  the  moun- 


68 


tain  for  a  distance  of  several  miles,  accompanied,  of  course,  by  a  great  volume  of 
ash,  as  in  the  case  of  all  the  previous  explosions.  These  blasts,  vertical  and  hori¬ 
zontal,  served  to  relieve  the  major  concentration  of  energy  developed  by  Lassen 
Peak  during  this  period  of  activity. 

VOLCANIC  BOMBS  AND  BRECCIA. 

On  the  saddle  between  Lassen  Peak  and  Lassen  Crags  to  the  northward  of  Lost 
Creek  Valley  there  were  found  a  considerable  number  of  small  fragments  which 
have  been  described  as  volcanic  bombs  because  of  the  evidence  of  recent  heat  which 
they  carry.  That  these  fragments  were  thrown  out  during  the  eruption  of  May  22 
there  appears  to  be  no  doubt.  Their  total  volume  is  insignificant.  They  were  of 
two  kinds:  (1)  a  sort  of  breccia  of  coarsely  pumiceous  material  containing  numerous 
inclusions  of  fragmentary,  unaltered  dacite  (fig.  36);  (2)  the  “bread-crust”  bombs. 


Fig.  36. — Pumiceous  material  containing  dacite  inclusions.  Photo  Snapp. 

The  pumiceous  material  in  appearance  is  hard  to  align  with  any  other  ejecta  dis¬ 
charged  during  this  entire  eruption,  neverthelesss  it  is  quite  common  along  the  path 
of  the  horizontal  blast.  It  is  a  very  light  pumice,  sometimes  hardly  more  than  a 
foam,  containing  large  bubbles  and  showing  plain  traces  of  superheating.  No 
other  comparable  material,  either  ancient  or  recent,  has  been  found  on  the  mountain 
in  so  far  as  we  are  aware.  In  color  the  pumice  varies  from  dark  purple  at  the  center 
through  many  shades  of  gray  to  yellow  on  the  outside,  representing  possibly  the 
variable  effect  of  oxidation  at  the  time  when  the  superheating  occurred.  The 
specimens  are  often  irregularly  banded  dark  and  light,  often  indicating  turbulent 
movement  in  the  liquid  state.  Inclusions  of  pumice  and  scoriaceous  matter  are 
numerous. 


69 


These  brecciated  masses  vary  in  size  from  2  feet  in  diameter  down  to  small 
fragments  of  a  few  inches,  and  none  were  observed  to  have  had  their  form  altered 
in  any  way  through  the  force  of  the  impact,  except  where  breakage  has  occurred, 
and  none  appear  to  have  been  altered  or  to  have  had  their  surface  configuration 
determined  in  any  way  by  their  flight  through  the  air.  These  facts  would  appear 
to  warrant  the  conclusion  that  they  were  no  longer  fluid  at  the  time  when  they  were 
thrown  out.  Perhaps  the  fact  that  no  material  has  been  found  on  the  summit 
from  which  these  could  have  been  detached,  contains  some  further  support  for  this 
conclusion.  Notwithstanding  this,  local  observers,  even  including  Loomis  and 
Diller,  are  of  the  opinion  that  in  these  fragments  we  have  direct  evidence  of  fluidity 
during  this  eruption.  To  us  it  seems  to  be  the  same  problem  over  again  which  con¬ 
fronted  us  in  studying  the  summit  material,  for  there  is  no  doubt  whatever  that  this 
material  was  once  fluid,  but  on  the  other  hand  no  evidence  has  been  found  that  it 
was  fluid  during  this  particular  eruption. 

BREAD-CRUST  BOMBS. 

The  second  group  of  fragments  is  found  associated  with  the  first  within  a 
small  area  of  a  few  acres  on  the  northeast  shoulder  of  the  mountain,  perhaps  a 
half  mile  distant  from  the  crater  bowl.  They  have  the  surface  appearance  of 
bread-crust  bombs,  but  in  no  case  do  they  show  the  symmetrical  forms  or  figures  of 
rotation  indicating  that  they  were  thrown  out  as  liquid  masses  whose  figure  was 
then  determined  during  flight.  Neither  is  there  among  these  fragments  any  evi¬ 
dence  of  splash  or  other  deformation  at  the  time  of  impact.  Nevertheless  the 
surface  is  a  true  bread-crust  surface  (fig.  37),  and  perfectly  fresh  as  though  it 
solidified  but  yesterday. 

Johnston-Lavis,  who  first  defined  bread-crust  bombs,  plainly  confined  his 
definition  to  liquid  ejecta,  of  which  the  general  form  was  more  or  less  determined 
during  flight,  and  accordingly  approximated  to  some  figure  of  rotation,  the  surface 
being  quickly  chilled  while  the  interior  was  still  liquid,  giving  the  bread-crust 
appearance  which  obviously  suggested  the  name.  Mercalli  a  year  later  adopted  the 
term  and  applied  it  to  a  great  number  of  bombs  which  had  figured  in  the  Italian 
eruptions.  The  type  is  more  or  less  familiar  to  all  students  of  volcanoes.  Hans 
Reck  has  brought  together  a  great  many  records  of  observations  of  these  bread- 
crust  bombs  and  has  sought  to  clarify  the  definition  in  an  elaborate  treatment  pub¬ 
lished  as  an  “ Erganzungsband ”  in  the  Zeitschrift  fur  Vulcanologie  in  1915  (q.  v). 
It  remained  lor  Lacroix  in  his  discussion  of  the  ejecta  from  Mont  Pelee  to  recognize 
a  new  group  which  belongs  in  this  classification,  but  which  had  not  hitherto  been 
included.  This  group  includes  random  fragments  of  solid  material  which  have  been 
superficially  reheated  by  gas  combustion  or  otherwise,  causing  the  surface  to  soften 
while  the  interior  remains  solid  and  unaltered.  The  surface  melting  serves  to 
develop  contraction  cracks  characteristic  of  the  bread-crust  surface,  which  may 
even  open  up  and  become  rounded  on  the  edges  if  the  exposure  is  long-continued. 
Such  bombs  retain  the  random  form  of  the  original  fragment,  which  is  of  course 
unaffected  by  flight  through  the  air. 


70 


Tb  is  second  group  of  fragments  found  on  the  northeast  slope  of  Lassen  Peak 
is  of  this  type;  some  are  somewhat  larger  than  the  brecciated  fragments  above 
described,  but  are  scattered  about  promiscuously  among  these.  They  are  for  the 
most  part  confined  to  this  area  and  have  only  occasionally  been  found  elsewhere  on 
the  mountain.  Unlike  the  pumiceous  fragments  such  bread-crusted  surfaces  are 
found  on  some  of  the  larger  fragments  at  the  summit  of  the  mountain,  showing 
possibly  the  local  development  of  considerable  heat  at  certain  points.  Inasmuch 
as  none  of  these  bread-crusted  surfaces  at  the  summit  appear  to  have  been  reheated 
in  their  present  position,  we  are  obliged  once  more  to  admit  a  reasonable  doubt 
whether  the  bread-crust  surface  was  acquired  during  this  eruption  or  some  earlier 
one. 

At  the  time  when  these  bombs  were  first  found  Lacroix’s  description  of  this 
type  had  not  come  to  the  attention  of  the  authors,  but  it  was  perfectly  clear  that 


Fig.  37. — July  17,  1913.  Bread-crust 
bomb  about  four  feet  long,  northeast 
slope  of  Lassen  Peak  about  one-half 
mile  from  crater.  Photo  Day. 

they  were  different  from  the  types  discussed  by  Reck  and  others  as  bread-crust 
bombs  on  account  of  their  generally  angular  shape  and  the  absence  of  any  influence 
upon  their  form  due  to  flight  through  the  air.  In  other  words,  they  were  evidently 
solid  fragments  at  the  moment  of  ejection  and  not  liquid  fragments,  so  that  although 
bread-crusted  on  the  surface  they  differed  fundamentally  from  the  hitherto  recog¬ 
nized  bread-crust  bombs.  Accordingly,  some  study  was  made  of  these  in  the  labor¬ 
atory,  and  in  particular  the  effort  was  made  to  produce  the  bread-crust  surface  on 
Lassen  Peak  dacite  which  had  been  sent  on  to  Washington  for  the  purpose.  Upon 
these  fragments  there  was  no  difficulty  in  producing  a  bread-crust  surface  after  an 
exposure  of  2  hours  to  a  temperature  of  iooo°.  Presumably  a  considerably  longer 
exposure  to  a  somewhat  lower  temperature  would  have  produced  the  same  results 
on  larger  masses. 

Th  ese  bread-crusted  surfaces  by  reason  of  their  extremely  fresh  appearance 
and  the  absence  of  contact  fracture,  such  as  might  have  been  expected  in  the 


71 


violence  of  the  explosion  through  which  they  passed,  may  possibly  have  been 
produced  during  this  eruption.  If  this  conclusion  is  adopted,  there  is  indication 
here  of  the  local  development,  presumably  in  very  small  areas,  of  a  temperature 
somewhat  higher  than  the  red  heat  noticed  and  reported  by  Milford  on  the  west 
slope  of  the  mountain.  A  red  heat  such  as  he  describes  would  not  be  adequate  to 
produce  bread-crust  surfaces  on  this  dacite  so  far  as  the  laboratory  experiment 
reveals  the  conditions  under  which  the  bread-crusting  must  have  occurred.  Some 
200°  additional  temperature  above  red  heat  are  necessary  to  produce  the  bread- 
crust  effects  here  observed.  On  the  other  hand,  the  very  small  quantity  of  such 
bread-crusting  which  has  appeared  at  the  surface  will  perhaps  indicate  that  these 
more  highly  heated  regions,  if  they  occurred  during  this  eruption  at  all,  are  re¬ 
stricted  to  a  few  small  openings,  presumably  in  the  deepest  part  of  the  crater  floor. 
The  ash  and  smaller  fragments  discharged  by  this  eruption  have  been  found  to 
contain  little  glass  or  even  rounded  crystalline  fragments. 

Dr.  H.  E.  Merwin  has  made  a  microscopic  examination  of  fragments  and  thin 
sections  of  the  bombs,  the  results  of  which  we  may  incorporate  here: 

1.  Very  vesicular  breccia  with  dark  andesitic  matrix  inclosing  various  vesicular  and 
porphyritic  rhyolites  and  andesites.  Some  of  the  fragments,  especially  the  denser  ones, 
are  very  loosely  held,  others  have  blended  and  flowed  with  the  matrix.  The  appearance 
suggests  that  the  matrix  was  formed  in  part  by  a  fluxing  of  the  most  basic  fragments  of  an 
original,  less  consolidated  breccia.  The  glass  of  the  matrix  is  more  basic  than  the  inclosed 
fragments — as  determined  by  refractive  index. 

I  have  not  found  more  than  traces  of  quartz  in  the  matrix,  but  it  is  abundant  in  some  of 
the  inclusions.  Biotite  scales  are  scattered  sparsely  in  the  matrix  and  inclusions,  and  it  is 
found  in  some  of  the  typical  andesites  of  the  region. 

Andesme  is  abundant  as  phenocrvsts  and  in  the  ground-mass. 

2.  Bomb  which  is  very  vesicular  but  only  obscurely  brecciated.  This  has  a  denser 
bread-crusted  surface,  contains  very  little  quartz  but  much  feldspar,  and  is  speckled 
sparsely  with  biotite.  The  biotite  scales  in  the  bread-crusted  surface  seem  unaltered.  One 
crack  was  observed  to  have  divided  a  biotite  flake  along  a  cleavage  and  the  sharp  edges  of 
the  biotite  remain. 

3.  Bomb  which  is  dense  and  aphanitic,  and  decidedly  bread-crusted.  This  is  a  typical 
dacite  with  considerable  quartz  and  andesine  as  phenocrysts.  Nothing  in  the  rock  powder 
examined  indicated  resorption  of  quartz,  but  slides  have  not  been  studied. 

The  phenocrysts  from  the  interior  of  bombs  are  almost  exclusively  fragments  of  plag- 
loclase  crystals.  Some  show  two  stages  of  growth  interrupted  by  a  period  of  resorption  or 
fracturing;  most  of  the  larger  phenocrysts  were  fractured  also  during  the  solidification  of 
the  bomb.  Original  flakes  of  biotite  are  largely  altered  to  dark,  very  fine-grained  aggre¬ 
gates  which  appear  to  consist  of  magnetite,  pyroxene,  feldspar,  and  glass.  The  cause  of 
the  alteration  is  not  apparent.  Quartz  is  almost  lacking. 


CHAPTER  IV. 

SOME  INFERENCES  CONCERNING  THE  CAUSES  OF  ACTIVITY. 

Now  that  we  have  brought  together  the  facts  of  observation,  both  those  which 
may  he  obtained  from  eyewitnesses  of  the  phenomena  and  those  which  may  be 
directly  inferred  from  conditions  which  are  visible  on  the  ground,  we  may  appropri¬ 
ately  inquire  about  the  relations  below  the  surface  which  determined  the  mechanism 
of  the  eruption,  and  perhaps  also  the  particular  conditions  which  may  have  precipi¬ 
tated  it. 

The  essential  facts  thus  far  determined  show  this  eruption  to  have  been  rather 
different  in  character  from  the  established  types  best  known  in  the  literature  of 
the  subject.  It  may  therefore  not  prove  practicable  to  determine  by  direct  analogy 
with  a  well-known  type  the  probable  relations  obtaining  in  this  eruption,  but  over 
against  this  limitation  we  may  set  the  fact  that  laboratory  and  theoretical  studies  of 
rock  formation  have  advanced  somewhat  farther  in  recent  years,  and  have  afforded 
information  regarding  the  behavior  of  the  fluid  magma  and  the  crystallization  of 
rock  from  it,  which  has  not  been  known  long  enough  to  find  particular  application 
to  the  earlier  eruptions.  Upon  this  information,  limited  though  it  is  at  present, 
we  may  profitably  draw  freely  for  the  elucidation  of  our  problem. 

Viewed  as  a  whole,  the  recent  eruption  of  Lassen  Peak  can  not  be  accounted 
a  volcano  problem  offering  great  complications.  The  phenomena  as  observed 
followed  a  reasonably  consistent  course  to  a  climax  without  serious  interruption  of 
continuity  and  without  the  intervention  of  unique  occurrences  like  the  appearance 
of  the  spine  in  the  crater  of  Mont  Pelee.  The  climax  itself  lasted  but  3  days  and 
was  without  catastrophic  complications  of  a  character  to  blind  observers  to  the 
normal  course  of  events,  or  to  interfere  with  a  reasonably  direct  deduction,  both  of 
the  proper  sequence  and  of  the  order  of  magnitude  of  the  manifestations  which 
occurred. 

The  closing  phases  following  upon  this  climax  have  indicated  nothing  more  than 
a  gradual  dying  down  of  the  active  forces  without  developing  any  features  of 
especial  interest.  The  facts  which  may  be  regarded  as  established,  upon  which 
attention  has  been  mainly  concentrated  in  the  foregoing  pages,  are  these: 

1.  A  period  of  the  order  of  magnitude  of  200  years  had  elapsed  since  the  last 
previous  activity  of  Lassen  Peak,  which  undoubtedly  gave  time  for  a  considerable 
accumulation  of  energy  beneath  the  plug  which  sealed  the  orifice.  During  recent 
years  no  fumarole  or  other  sign  of  latent  activity  has  been  visible  on  the  mountain, 
so  that  the  volcano  may  be  regarded  as  having  been  completely  sealed.  Also,  we 
may  not  overlook  the  fact  that  the  hot  zone  approaches  close  to  the  surface  in  this 
region,  as  is  evidenced  not  only  by  the  activities  of  the  volcano  itself,  but  also  by  the 
continuous  activity  of  the  near-by  hot  springs,  of  which  there  are  several  groups 
extending  along  the  south  front  of  the  mountain  and  to  the  southeastward  for  a 

72 


73 


distance  of  io  miles  (see  Part  II).  This  is  also  the  major  zone  of  faulting,  as  has 
been  shown  by  the  detailed  studies  of  the  geology  of  the  region  recently  undertaken 
by  Diller  (unpublished). 

2.  The  lava  forming  the  plug  of  Lassen  Peak,  as  well  as  the  inclosing  cone,  is 
dacite  of  somewhat  variable  composition,  which  does  not  differ  from  the  neighboring 
andesite  in  chemical  content,  but  does  differ  from  it  frequently  in  mineral  composi¬ 
tion  in  that  it  usually  contains  small  quantities  of  free  quartz.  The  composition  of 
this  dacite  and  its  relation  to  andesite  are  in  this  particular  very  like  the  correspond- 


Fig.  38.—  May  22,  1913.  A  view  of  the  great 
eruption  from  Mineral,  12  miles  south 
of  Lassen  Peak.  Photo  Hampton. 


ing  lavas  participating  in  the  latest  eruption  of  Mont  Pelee  (1902),  which  have 
been  studied  in  great  detail  by  Lacroix.1  It  will  be  worth  while  to  recall  in  this 
connection  that  Lacroix’s  conclusion  was  that  the  dacite  appeared  wherever  condi¬ 
tions  were  favorable  for  slow  crystallization,  while  the  andesite  may  have  resulted 
from  more  rapid  cooling. 


1  A.  Lacroix,  LaMontagne  Pelee  et  ses  Eruptions.  1904. 


74 


3.  The  volcanic  phenomena  throughout  the  recent  period  of  activity  have 
yielded  no  evidence  of  high  temperatures,  near  the  surface  at  least,  nor  of  the 
participation  of  any  considerable  quantities  of  the  chemically  active  gases  such  as 
are  commonly  found  in  the  volcanoes  in  which  temperatures  are  high.  In  the 
absence  of  evidence  of  oxidation  of  any  of  the  participating  components,  whether 
gaseous  or  other,  it  may  fairly  be  assumed  that  there  was  no  chemical  activity  of  a 
kind  to  add  heat  to  the  system.  The  explosions,  so  far  as  direct  observations  can 
determine  their  character,  were  primarily  of  steam,  more  or  less  laden  with  ash 
(figs.  39,  40)  from  the  crater  bowl  or  produced  by  attrition  in  the  conduit.  None 


Figs.  39,  40. — The  great  eruption  of  May  22,  1915,  viewed  from  Mineral  12  miles 
south.  Photo  Hampton. 

was  violent  enough  to  change  the  form  of  the  cone  or  even  to  dislodge  any  consider¬ 
able  sections  of  it.  The  highest  temperature  indicated  either  by  indirect  or  by  dir¬ 
ect  observation  was  a  moderate  red  heat  which  can  not  have  been  more  than  700°  or 
8oo°.  Very  locally  there  may  have  been  slightly  higher  temperatures  if  the  brec- 
ciated  fragments  and  the  little  group  of  bread-crust  bombs  were  formed  during  this 
eruption,  but  this  conclusion  is  open  to  question.  There  was  no  conclusive  evidence 
of  glow  on  the  mountain  except  on  the  night  of  May  19  during  the  short  culmina¬ 
tion  of  the  activity,  nor  were  red-hot  fragments  certainly  observed  on  any  other 
occasion.  There  were  also  no  more  than  two  or  three  occasions  when  chemically 


75 


active  gases  were  certainly  detected,  and  then  only  in  small  quantity  and  for  short 
periods.  No  evidence  was  found  of  the  destruction  of  foliage  by  gases,  as  is  so 
frequently  seen  at  Vesuvius,  where  acres  of  trees  and  smaller  plants  are  sometimes 
completely  blasted  in  a  few  hours’  exposure  to  a  smoke  cloud  so  cold  that  it  will  not 
even  rise  but  “rolls”  down  the  mountainside. 

4.  The  two  great  floods  and  the  minor  mud  flows,  which  are  so  conspicuous 
among  the  visible  evidences  of  activity,  and  in  consequence  have  played  such  a 
considerable  part  in  the  descriptions  of  the  eruption  of  Lassen  Peak  in  the  news¬ 
papers  and  popular  literature,  may  be  dismissed  as  secondary  effects,  due  to  the 
condensed  steam  tailing  upon  a  great  body  of  accumulated  snow  and  set  in  motion 
by  hot  horizontal  blasts  from  the  mountain. 

5.  The  only  lava  movement  en  masse  occurring  during  this  eruption  period 
was  the  lifting  of  the  lava  plug  forming  the  old  crater  floor  into  a  position  nearly 
level  with  the  crater  rim,  an  elevation  of  at  least  300  feet,  following  the  faulting  of 
the  summit  cone  which  began  at  or  before  the  first  eruption  in  1914  and  continued 
to  grow  under  the  stress  of  the  explosions  until  the  plug  was  lifted  to  fill  both  the 
rift  and  the  explosion  crater.  Whether  in  lifting  the  plug,  a  movement  taking  place 
entirely  within  the  cone,  liquid  lava  from  below  would  become  exposed  is  of  course 
entirely  a  matter  of  accident.  The  upward  movement  stopped  when  the  crater 
floor  had  reached  the  level  of  the  rim,  so  that  the  liquid  lava  could  not  become 
exposed  unless  the  plug  should  be  shattered  or  the  cone  itself  yield  to  the  force  of  the 
explosions  at  some  point  of  weakness.  The  cone  did  yield  at  three  points:  (1)  Along 
the  fault-line  on  the  northeast  side,  where  the  two  horizontal  blasts  emerged,  but 
this  opening  appears  to  have  come  just  under  the  “lid”  which  closed  down  upon  it 
immediately  afterward,  so  that  its  precise  position  can  only  be  inferred  from  local 
fumaroles.  It  is  near  this  point,  however,  that  an  instance  of  recent  flow  in  situ 
was  found.  There  is  also  an  opening  (2)  on  the  north  front  of  the  cone  extending 
radially  down  the  mountain  for  several  hundred  feet  from  a  point  very  near  the 
summit,  through  which  a  considerable  number  of  the  later  explosions  were  seen  to 
emerge,  but  no  evidence  of  heat  concentration  or  of  liquid  lava  has  been  seen  there. 
The  third  opening  is  the  rift  in  the  western  rim  which  was  filled  when  the  plug  was 
lifted.  All  of  these  openings  are  in  or  about  the  crater  rim  and  so  gave  no  oppor¬ 
tunity  for  the  release  of  fluid  lava  from  beneath  the  plug. 

6.  So  far  as  available  observation  goes,  all  the  explosions  recorded,  both 
vertical  and  horizontal,  were  steam  explosions,  so  that  water  appears  to  be  the  only 
volatile  ingredient  with  which  we  have  to  deal  seriously  as  a  possible  participating 
cause.  Ground-water  levels  were  high  and  a  number  of  streams  of  considerable  size 
have  their  sources  high  up  on  the  mountain.  The  annual  rainfall  at  the  nearest 
comparable  station  (Inskip)  is  upwards  of  80  inches.  The  accumulation  of  snow  in 
the  crater  bowl  was  melting  rapidly  at  the  beginning  of  the  activity  in  May  1914 
and,  except  for  the  small  portions  blown  out  during  the  explosions  themselves, 
contributed  directly  to  the  water  content  of  the  volcano.  This  supply  of  snow 
was  exhausted  during  July  1914  and  a  new  and  uncommonly  large  accumulation 
replaced  it  during  the  following  winter.  Following  the  two  winter  seasons  (1913  14, 


76 


1 9 1 5 ) ?  therefore,  a  great  amount  of  meteoric  water  undoubtedly  reached  the 
volcano  hearth  (as  steam)  directly  through  cracks  in  the  plug  (crater  floor). 

Bringing  this  evidence  to  bear  upon  the  problem  of  the  actuating  forces,  we 
have  to  consider  the  relation  between  water  and  the  characteristic  andesite  lava  at 
temperatures  below  iooo°.  Thus  far  we  have  considered  only  facts  of  direct 
observation  or  of  immediate  inference  therefrom.  It  is  now  necessary  to  make 
assumptions  to  which  a  reasonable  degree  of  probability  can  be  assigned.  The  first 
is  that  we  are  dealing  with  a  cooling  system,  that  is  to  say,  a  mass  of  magma  which 
is  receiving  no  new  heat,  as  for  example  by  chemical  action  during  the  eruption. 
Energy  accumulated  during  two  centuries  under  a  perfect  seal  is  finding  release,  not 
at  once,  but  gradually  over  a  period  of  several  years.  What  conditions  and  rela¬ 
tions  are  competent  to  accumulate  and  localize  this  energy  in  a  slowly  cooling 
system  and  to  release  it  explosively  in  this  manner? 

Beneath  the  plug  there  is  undoubtedly  a  considerable  mass  of  liquid  magma  in 
which  some  crystallization  has  taken  place,  inclosed  within  a  cone  of  the  same 
material.  We  have  little  information  upon  which  to  base  an  appraisal  of  its  con¬ 
dition  at  the  temperature  now  prevailing  in  it,  except  that  the  solidified  lava  now 
exposed  still  contains  some  glass  and  also  free  quartz,  the  latter  of  which  has  been 
shown  (Lacroix,  op.  cit.)  to  indicate  a  very  slow  crystallization  of  the  andesite 
magma. 

The  presumption  is,  further,  that  the  movement  of  the  plug  at  this  compara¬ 
tively  low  temperature,  through  upthrust  of  liquid  magma  from  below,  is  positive 
indication  that  the  water  content  of  the  liquid  lava  is  large,  otherwise  there  is  little 
possibility  of  fluid  movement  in  a  magma  of  this  composition.  This  is  further 
established  by  direct  inference  from  the  immense  quantities  of  water  given  off  during 
the  explosions  throughout  all  phases  of  activity,  and  is  otherwise  logical  because  of 
the  high  level  of  the  hot  zone  in  a  region  of  considerable  rainfall.  It  is  logical  also 
because  a  lava  high  in  silica  will  probably  carry  in  solution  more  water  than  a  basic 
lava,1  and  also  because  all  volatile  ingredients,  other  conditions  being  equal,  tend 
to  be  driven  off  by  heat,  and  therefore  the  lower  the  temperature  the  greater  the 
possible  content  of  volatile  matter  (in  this  case  water)  in  the  magma. 

G.  W.  Morey  has  recently  published  a  paper  in  which  these  questions  are 
considered  in  some  detail.2  Almost  all  of  this  bears  upon  the  question  here  under 
discussion,  and  considerable  citations  from  it  will  therefore  be  permissible.  He  says, 
for  example,  of  the  solubility  of  molten  lavas  for  water  vapor  the  following: 

It  is  now  a  demonstrated  fact  that  water  vapor  under  a  pressure  of  one  atmosphere 
is  appreciably  soluble  in  liquid  silicates  at  their  melting-points,  and  that  the  amount  of 
water  dissolved  at  this  pressure  will  produce  an  appreciable  lowering  of  the  melting-point. 

.  .  .  If  the  initial  pressure  of  water  vapor  is  increased,  more  water  will  be  dissolved 
and  freezing  will  begin  at  a  correspondingly  lower  temperature. 

The  solubility  of  water  in  a  silicate  melt  at  a  given  pressure  of  water  vapor  will  depend 
largely  on  the  temperature,  and  it  is  to  be  expected  that  the  solubility  will  increase  with 


1  See  below. 

2  G.  W.  Morey,  Development  of  pressure  in  magmas  as  a  result  of  crystallization,  Journ.  Wash.  Acad.  Sci.  12.  219,  1922. 


77 


decreasing  temperature,  for  the  same  reasons  that  gases  are  more  soluble  in  cold  water  than 
in  hot  water.  If  an  undercooled  silicate  mixture,  that  is,  a  mixture  which  had  remained 
liquid  although  it  had  cooled  below  the  temperature  at  which  crystallization  should  have 
taken  place,  were  to  come  into  contact  with  water  vapor,  ...  it  would  probably  take 
up  a  much  larger  quantity  of  water  than  at  a  high  temperature. 

The  evidence  which  has  led  Morey  to  these  conclusions  is  partly  derived  from 
general  laws  of  solutions  which  have  now  received  abundant  verification  and  partly 
from  actual  experimentation  with  molten  salts  and  silicates.  They  may  therefore 
be  accepted  as  bearing  directly  upon  our  problem  and  offering  information  of  funda¬ 
mental  importance.  We  conclude  from  it  at  once  that  the  highly  siliceous  magma 
beneath  the  plug  almost  certainly  contained  great  quantities  of  water  in  solution, 
and  that  its  mobility  at  this  relatively  low  temperature  was  directly  the  result  of 
this  water  content.  A  high-silica  magma  without  water  is  ultraviscous. 

If  it  is  desirable  to  offer  direct  geological  evidence  to  supplement  that  of  the 
laboratory  upon  the  capacity  of  a  highly  siliceous  magma  to  carry  water  in  solution, 
it  will  be  borne  in  mind  that  some  obsidians  and  pitchstones,  of  whose  analyses  we 
have  a  record,  are  found  to  contain  io  per  cent  or  more  of  water,1  while  average 
andesites,  according  to  Washington’s  table  of  analyses,  contain  no  more  than  from 
i.o  to  1.5  per  cent  of  water.  Pitchstones  and  obsidians  are  really  liquid  magma 
which  has  cooled  down  under  such  extraordinary  conditions  that  true  freezing  (crys¬ 
tallization)  did  not  occur.  Any  readjustment  of  relations  leading  to  equilibrium 
between  the  volatile  and  non-volatile  elements  of  such  a  magma  was  therefore 
prevented,  and  we  have  in  these  unusual  masses  a  trustworthy  picture  of  a  liquid 
magma  before  the  volatile  elements  are  driven  out  by  subsequent  reactions. 

From  the  evidence  of  the  laboratory,  therefore,  as  well  as  from  natural  occur¬ 
rences,  the  conclusion  is  justified  that  the  Lassen  Peak  magma  was  fluid  at  such 
low  temperature  because  of  the  amount  of  water  in  solution  in  it,  and  the  fact  that 
movement  occurred  at  all  at  these  temperatures  is  direct  evidence  of  high  water- 
content. 

So  far  as  this  conclusion  is  concerned  it  is  immaterial  whether  the  water  is 
an  original  constituent  of  the  magma,  or  is  meteoric  water  acquired  in  the  usual 
way  through  contact  with  water-bearing  strata,  or  is  meteoric  water  reaching  the 
volcano  hearth  through  cracks  in  the  crater  floor  under  a  head  determined  by  the 
elevation  of  the  crater  basin. 

The  last  source  alone  would  probably  be  inadequate  to  provide  all  or  even  a 
considerable  proportion  of  the  water  given  off  in  the  300  or  more  explosions  con¬ 
stituting  the  present  activity  of  Lassen  Peak  (pp.  176,  et  seq ),  but  it  may  not  be 
neglected  as  one  of  the  sources  of  the  great  quantity  of  water  that  participated  in  and 
was  indeed  responsible  for  the  activity.  The  water  was  undoubtedly  supplied  from 
all  the  three  sources  mentioned.  The  point  of  chief  interest  here  is  not  a  distribution 
as  between  available  sources  of  supply,  but  the  establishment  of  adequate  sources 
for  the  tremendous  quantities  given  off. 

1  Cf.  J.  W.  Judd  et  al.  The  Eruption  of  Krakatoa  and  Subsequent  Phenomena,  p.  36.  (Rept.  of  Krakatoa  Com. 
Roy.  Soc.  London  1888.)  . 


78 


Suppose  we  consider  now  the  effect  of  the  progress  of  crystallization  in  a 
magma  of  this  type  under  the  conditions  above  described.  This  is  the  major  subject 
of  discussion  in  Morey’s  paper,  from  which  we  may  therefore  appropriately  quote 
further: 

At  temperatures  near  that  at  which  crystallization  begins,  a  liquid  silicate  mixture 
containing  but  a  small  amount  of  volatile  component  may  exert  but  a  comparatively  small 
vapor  pressure,  but  as  crystallization  proceeds  with  falling  temperature  the  pressure  of  the 
volatile  components  will  increase  at  a  rapid  rate,  so  rapid  that  a  pressure  many  times  the 
original  pressure  may  result  from  the  crystallization  of  but  a  small  proportion  of  the  non¬ 
volatile  material. 

The  logic  of  this  conclusion  is  direct  and  inevitable,  for  as  the  magma  crystal¬ 
lizes  the  volatile  ingredients  are  crowded  out,  and  if  they  are  then  confined  in  a 
closed  space  their  pressure  will  increase  rapidly  until  relieved  by  rupture  of  the  in¬ 
closure  or  otherwise.  This  accounts  at  once  for  the  gradual  accumulation  of 
energy  in  such  a  closed  volcanic  hearth,  where  the  only  operative  cause  required 
is  a  sufficient  water  content  and  the  gradual  cooling  and  crystallization  of  the  mag¬ 
ma  contained  therein.  Morey  illustrates  this  by  a  number  of  laboratory  studies 
beginning  with  the  behaviour  of  crystallizing  potassium  nitrate  and  water,  the 
progress  of  which  can  be  followed  in  detail,  he  says: 

As  the  mixture  cools,  crystallization  proceeds,  the  water  content  of  the  liquid  in¬ 
creases,  and  its  vapor  pressure  rises.  Reference  to  figure  [41]  a  or  b1,  shows  that  at  the  time 
crystallization  begins  the  liquid  composition  is  99  per  cent  KN03,  1  per  cent  H20.  When  the 
water  content  has  doubled,  the  pressure  has  increased  from  1  atmosphere  to  over  6  atmos¬ 
pheres,  a  six-fold  increase.  When  the  water  content  has  again  doubled,  reaching  4  per 
cent,  the  pressure  has  risen  to  almost  11  atmospheres.  If  the  mixture  be  contained  in  a 
flask  which  can  withstand  a  pressure  of  only  10  atmospheres,  the  flask  will  burst  as  the 
result  of  the  pressure  developed  by  cooling  the  mixture. 

1 1  igure  41. 


A  B 

Fig.  41 . — Diagrams  showing  change  of  pressure,  temperature,  and  compo¬ 
sition' of  thefunivariant  "equilibria  between  solid,  liquid,  and 
vapor  phases  in  the  binary  ^system  H2O-KNO3. 


79 


A  further  example,  illustrating,  from  the  experimental  results,  the  development  of  a 
fairly  high  pressure  in  a  silicate  system  as  the  result  of  cooling,  may  be  found  in  the  same 
system  [H20—  K2Si03—  Si02].  The  eutectic  between  K2Si205  and  Si02  lies  at  the  remark¬ 
ably  low  temperature  of  520°.  If  a  mixture  of  K20,  Si02  and  H20,  containing  9.1  per  cent 
of  H20,  with  the  other  ingredients  in  the  molecular  ratio  Si02/K20  =  4.26,  be  cooled  from 
a  high  temperature,  the  vapor  pressure  of  the  mixture  will  fall  as  the  temperature  falls. 
The  mixture  will  not  begin  to  freeze  until  it  has  cooled  to  500°,  when  crystals  of  quartz 
and  the  ternary  compound  KHSi205  will  separate.  The  vapor  pressure  of  the  solution  at 
this  temperature  is  160  atmospheres.  On  further  cooling  the  substances  continue  to 
crystallize  and  the  pressure  increases  rapidly.  When  the  temperature  has  fallen  20°,  to 
480°,  the  water  content  has  increased  to  10.2  per  cent,  and  the  pressure  to  180  atmospheres. 
When  the  temperature  has  fallen  to  420°,  the  water  content  has  increased  to  12.5  per  cent 
and  the  pressure  to  340  atmospheres,  more  than  double  the  pressure  at  500°. 

It  is  of  interest  to  consider  what  would  happen  if  the  mixture  were  to  cool  without 
ciystallizing,  say  to  420°,  and  then  begin  to  crystallize.  .  .  .  On  the  assumption  that 
the  drop  in  pressure  for  the  8o°  drop  in  temperature  from  500  0  to  420°  in  the  solution  is  the 
same  as  the  drop  in  pressure  of  water  from  348°  to  a  temperature  8o°  lower,  the  vapor 
pressure  of  the  supercooled  liquid  at  420°  will  be  59  atmospheres.  If  the  mixture  containing 
9.1  per  cent  water  were  to  cool,  without  crystallizing,  from  500°,  its  saturation  temperature, 
to  420°,  its  pressure  would  fall  from  160  atmospheres  to  about  50  atmospheres.  If  at  this 
lower  temperature  it  should  begin  to  crystallize,  the  pressure  would  suddenly  rise  to  that  of 
the  solution  in  equilibrium  with  quartz  and  HKSi205  at  420°,  or  340  atmospheres. 

It  is  evident,  then,  that  as  a  magma  containing  water  and  other  volatile  components 
cools,  with  consequent  crystallization,  the  pressure  will  rapidly  rise  from  its  initial  value, 
and  as  the  cooling  continues  the  pressure  will  increase  until  the  temperature  of  maximum 
pressure  has  been  reached,  or  until  the  pressure  is  relieved  by  escape  of  the  volatile  material. 
In  the  first  case,  which  is  that  in  which  the  liquid  cools  under  a  crust  of  sufficient  weight  and 
strength  to  withstand  the  internal  pressure,  the  liquid  will  solidify  as  an  intrusive  mass. 

If  the  vent  is  a  fairly  open  one,  enormous  pressures  probably  will  not  be  developed 
and  the  escape  of  the  water  as  steam  may  be  comparatively  quiet;  ...  It  may  well 
be  that  in  both  these  cases  the  activity  is  the  result  of  the  release  of  volatile  material  conse¬ 
quent  on  crystallization,  and  the  rate  of  release  of  the  volatile  material  may  be  regarded 
as  a  measure  of  the  rate  of  crystallization  in  the  parent  body. 

In  the  last  paragraph  of  this  discussion  lies  a  clue  to  the  character  and  develop¬ 
ment  of  the  present  eruptive  activity  which  we  may  not  overlook.  If  the  rapidity 
of  release  of  water  from  the  magma  is  proportional  to  the  rate  of  crystallization  and 
the  increasing  pressure  of  this  water  vapor  is  the  explosive  agent,  the  appearance  of 
outbreaks  at  intervals  of  2  or  3  days  during  the  entire  summer  and  autumn  of  1914 
is  readily  explained.  If  the  explosions  had  been  due  only  to  water  from  without, 
pouring  into  rifts  in  the  crater  floor,  and  exploding  as  steam  on  reaching  the  hot 
zone,  no  such  periodicity  extending  into  the  summer  and  autumn  would  have  been 
possible.  Consideiing  the  explosions  to  be  due  to  a  more  or  less  regular  release  ot 
water  vapor  from  a  crystallizing  magma,  to  which  any  outside  water  is  merely  con¬ 
tributory,  then  explosions  may  be  expected  to  occur  as  often  as  the  accumulating 
pressure  within  overcomes  the  resistence  of  the  envelope.  Usually  it  may  be 
assumed  that  the  inclosing  crater  wall  will  withstand  the  expanding  force  of  the 
volatile  ingredients  released  by  the  magma,  and  the  outbreaks  will  then  depend 
solely  upon  the  fortuitous  resistance  of  the  conduit  and  its  contents  to  the  accumu- 


80 


lating  pressure  from  below.  Morey,  in  his  subsequent  treatment,  recognizes  the 
cumulative  character  of  this  operation  and  its  direct  bearing  upon  the  eruptive 
period.  He  says: 

Conditions  may  be  such  that  a  much  greater  pressure  must  be  developed  before  the 
gases  are  able  to  force  their  way  to  the  surface.  It  may  be  assumed  that  eruptions  will 
then  take  place  at  less  frequent  intervals. 

Such  accumulating  pressures  may  find  release  in  a  single  explosion,  like  Bandai- 
san,  or  explosions  may  come  intermittently  over  a  considerable  interval  of  time, 
as  happened  at  Mont  Pelee  or  in  the  case  now  under  consideration,  where  explosions 
continued  to  recur  over  a  period  of  more  than  4  years.  Indeed,  so  far  as  the  theory 
is  concerned  it  is  direct,  competent,  and  appears  to  require  no  modification  beyond 
the  local  limitations  imposed  by  varying  composition  of  the  magma,  the  water 
supply,  and  the  physical  resistance  of  the  structure.  When  a  conduit  is  once  opened 
consecutive  explosions  at  longer  or  shorter  intervals  from  the  same  opening  are 
likely,  for  the  probability  is  small  that  the  volcano  hearth  will  be  laid  wide  open 
by  a  single  explosion,  or  the  accumulated  pressure  otherwise  completely  discharged 
in  the  first  outbreak.  Where  a  considerable  body  of  magma  participates  and  the 
more  fluid  portions  have  access  to  the  opening  a  lava  flow  may  result,  following 
somewhat  the  same  mechanism  as  a  soda-water  bottle  when  the  entire  content  is 
violently  discharged  through  a  too  abrupt  relief  of  the  pressure.  Or  an  open  stand 
of  fluid  lava  may  accumulate  in  the  conduit,  discharging  its  gas  content  by  quiet 
bubbling,  with  or  without  occasional  overflows,  as  at  Vesuvius  before  the  outbreak 
of  1906  and  at  the  present  moment,  or  as  at  Kilauea  usually.  All  these  conditions 
find  a  ready  explanation  through  the  same  mechanism,  with  but  slight  modifica¬ 
tions  of  local  mechanical  details. 

With  very  great  volcanoes,  such  as  Mauna  Loa  in  Hawaii  or  Etna  in  the 
Mediterranean,  the  point  where  the  structure  fails  under  the  cumulative  pressure 
is  usually  not  the  summit  crater,  but  some  other  point  lower  down,  where  weakness 
has  developed  through  Assuring  or  some  other  mechanical  defect,  or  because  of  the 
solvent  action  of  the  magma  boring  from  within.  In  these  cases  the  hydrostatic 
pressure  of  the  overlying  column  in  the  conduit  is  probably  added  to  that  developed 
in  the  crystallizing  magma  below.  There  is  evidence  at  Mauna  Loa  that  the  whole 
mountain  becomes  distended  as  the  pressure  develops  prior  to  a  catastrophic 
release;  also  that  there  is  some  segregation  due  to  gravity  in  the  great  magma 
chamber,  for  outbreaks  at  or  near  the  summit  release  either  gas  alone  or  a  light 
emulsion,  while  outbreaks  at  lower  levels  are  flows  of  heavy  lava  containing  little 
gas.  The  difference  in  level  between  the  summit  crater  and  the  recent  lava  out¬ 
pourings  at  Mauna  Loa  is  about  7,000  feet. 

All  these  are  but  instances  of  local  limitations  impressed  upon  the  pressure 
reservoir,  which  have  the  effect  of  varying  rather  radically  the  visible  phenomena  of 
volcanic  outbreaks  without  in  any  way  affecting  the  application  of  the  simple 
theory  here  offered  to  account  for  the  continuing  source  of  pressure,  so  long  as  the 
crystallization  of  the  magma  remains  incomplete.  The  limiting  condition  at  Lassen 
Peak,  and  from  a  theoretical  viewpoint  its  most  interesting  feature,  was  the  un- 


81 


commonly  low  temperature  at  which  the  more  violent  phases  developed.  It  is 
altogether  conceivable  that,  if  the  temperature  had  been  but  a  little  lower,  ultra¬ 
viscosity  would  have  spread  its  inert  mantle  over  the  whole  system  and  no  move¬ 
ment  would  have  occurred,  however  remote  the  solution  was  from  a  condition  of 
equilibrium.  Perhaps  the  Obsidian  Cliff  of  Yellowstone  Park  is  as  good  an  illustra¬ 
tion  as  can  be  found  of  a  frozen  system  in  which  equilibrium  was  never  reached. 

There  is  still  another  phase  in  the  theoretical  consideration  of  this  subject  which 
may  have  a  bearing  on  conditions  at  Lassen  Peak,  though  experimental  evidence  is 
limited  by  the  fact  that  no  flow  occurred  and  no  sample  of  lava,  which  certainly 
represents  the  present  stage  of  development  within  the  magma  basin,  has  been  col¬ 
lected.  We  quote  again  from  Morey: 

It  might  be  that,  if  the  crust  were  of  sufficient  strength,  a  fairly  large  proportion  of  the 
liquid  magma  would  crystallize  before  a  pressure  had  been  built  up  of  sufficient  magnitude 
to  cause  an  eruption  ...  In  such  a  case,  in  which  a  considerable  amount  of  crystalliza¬ 
tion  has  taken  place,  the  non-crystallized  material  ejected  will  represent  the  “mother 
liquor”  remaining  after  the  segregation  of  those  minerals  which  are  the  first  to  crystallize 
under  the  conditions  prevailing.  These  may  be  the  femic  minerals,  in  which  case  the 
mother  liquor  will  he  enriched  in  the  more  salic  minerals,  quartz  and  the  feldspars,  and  the 
water  content  will  be  correspondingly  increased.1 

The  tendency  for  the  heavier  femic  minerals  to  differentiate  by  settling  will  be  great, 
especially  since  the  density  difference  between  the  femic  and  salic  minerals  will  be  increased 
by  the  presence  in  the  salic  melt  of  the  accumulated  water. 

To  make  appropriate  application  of  this  indication  would  lead  us  out  upon 
broader  ground  than  is  contemplated  in  the  direct  consideration  of  the  outbreak  at 
Lassen  Peak.  It  will  be  recalled,  however,  that  Differ  definitely  included  Lassen 
Peak,  geologically,  within  the  great  region  of  basaltic  overflow  extending  through 
portions  of  five  states  in  the  great  Northwest.  Lassen  Peak  is  one  of  the  few 
remaining  active  vents  in  this  entire  region,  and  therefore,  presumably,  contains  the 
last  vestiges  of  residual  magma.  Aurousseau  has  also  characterized  this  lava  as 
“well  differentiated”  (p.  40).  Very  probably  this  segregation,  to  which  Bowen  first 
called  attention  in  the  paper  to  which  reference  has  been  made,  is  responsible  for 
the  depletion  of  basalt  (the  femic  minerals)  in  the  residual  magma  in  this  great 
volcanic  basin,  and  the  persistence  of  salic  residues  stiff  fluid  because  of  their  high 
water  content. 

A  final  and  very  short  paragraph  may  properly  concern  itself  with  the  assign¬ 
ment  of  a  possible  cause  to  this  particular  outbreak.  Of  course,  the  ultimate 
cause  is  to  be  sought  and  found  in  the  accumulation  of  sufficient  pressure  to  break 
down  the  overlying  resistance  of  the  plug  which  closed  the  original  conduit.  This 
may  be  due  either  to  the  continuity  of  pressure  development  in  the  manner  indi¬ 
cated,  which  finally  equaled  and  overcame  the  overlying  resistance;  or  it  may 
happen  that  this  resistance  was  broken  down  or  weakened  through  the  operation  of 
some  extraneous  cause,  thereby  giving  an  opportunity  for  release  to  the  accumu¬ 
lated  vapor  pressure  within.  There  is  some  indication  that  the  latter  explanation 
is  the  true  one.  The  fact  that  cracks  over  100  feet  long  and  in  the  general  direction 

1  N.  L.  Bowen,  Later  stages  of  the  evolution  of  the  igneous  rocks,  Journ.  Geol.  Suppl.,  vol.  23,  No.  8,  1915. 


82 


of  the  summit  fault  were  noticeable  immediately  after  the  first  explosion  and  were 
reported  in  the  very  first  telegram  announcing  the  inception  of  activity,  (p.  3) 
appears  to  warrant  the  consideration  of  such  a  possibility. 

Whether  these  two  cracks  represented  the  first  outbreak  of  a  cumulative  pres¬ 
sure,  or  an  earthquake  disturbance  which  weakened  the  volcano  plug,  is  a  question 
to  which,  probably,  no  direct  answer  can  be  given.  It  is  a  fact,  however,  that  the 
first  explosion  was  insignificant  in  point  of  magnitude  and  altogether  inadequate 
to  account  for  the  cracks.  If  it  had  represented  the  first  outbreak  of  enormous 
pressure  accumulated  through  200  years  or  more  of  slowly  crystallizing  magma 
then  breaking  through  the  crust  for  the  first  time,  a  catastrophic  explosion  would  be 
expected  and  the  explosions  following  would  be  weaker;  or  a  long  pause  might  ensue, 
for  the  volcano  hearth  itself  would  probably  be  laid  open. 

If  on  the  other  hand  the  first  opening  represented  a  weakening  of  the  plug  from 
without,  the  resistance  of  which  then  required  to  be  broken  down  and  the  opening 
enlarged  from  within,  successive  explosions  of  progressively  increasing  magnitude 
would  seem  to  be  a  natural  consequence.  If  the  latter  conclusion  is  followed,  the 
water,  which  entered  the  cracks  after  the  first  and  subsequent  explosions,  may 
have  been  a  very  definite  contributing  cause,  for  a  considerable  influx  of  water  from 
without  might  cause  a  considerable  increase  of  fluidity  locally,  and  so  precipitate 
activity  in  a  more  or  less  inert  mass.  Morey  says  of  this  phase  of  the  subject  in 
his  theoretical  exposition: 

If  an  undercooled  magma  were  to  come  into  contact  with  percolating  waters,  or  the 
vapor  generated  thereby,  as  previously  explained,  a  similar  introduction  of  water  at  a  low 
pressure  might  take  place.  Introduction  of  this  water  might  of  itself  induce  crystallization 
in  virtue  of  the  lowered  viscosity  of  the  resulting  magmatic  solution,  and  it  is  conceivable 
that  the  result  would  be  a  sudden  and  violent  outburst  of  steam  and  ash,  at  a  comparatively 
low  temperature. 

If  the  weakening  of  the  inclosing  plug  came  from  without  and  water  was 
admitted  to  contact  with  the  outlying  portions  of  a  magmatic  mass  in  which  reaction 
had  practically  ceased  and  a  condition  of  suspended  activity  in  an  ultraviscous 
magma  had  supervened,  then  the  relation  indicated  by  Morey  might  be  realized. 
The  influx  of  water-vapor  from  above  into  the  outlying  portions  of  an  incompletely 
crystallized  magma  might  then  have  the  effect  of  decreasing  viscosity  in  the  still 
fluid  portion  and  promoting  crystallization,  and  might  cause  an  explosion  which 
would  be  followed  by  others  in  increasing  intensity  as  greater  bodies  of  magma 
were  affected  by  the  more  favorable  conditions.  This  mechanism  seems  to  offer  a 
more  logical  explanation  of  a  series  of  explosions  of  progressively  greater  intensity, 
and  approaching  a  culmination  after  several  months,  than  any  other  which  has 
been  suggested. 

To  those  who  are  accustomed  to  draw  upon  experience  with  solutions  of  salts 
in  water  for  precedents  of  convenient  application  here,  a  word  of  suggestion  may 
help  to  clear  up  certain  misgivings  which  can  hardly  fail  to  come  to  mind  in  following 
the  demonstration  just  offered.  Undercooling  in  salt  solutions  is  rare  and  can 
hardly  occur  in  contact  with  crystals  of  the  stable  solid  phase.  Because  of  the 


83 


great  viscosity  of  silicate  solutions  (magmas)  undercooling  is  there  the  rule,  and 
furthermore,  the  rate  of  reaction  is  often  extremely  slow,  so  that  equilibrium 
throughout  any  considerable  mass  of  magma  can  not  be  expected  to  follow  shifting 
conditions,  nor  indeed,  in  a  magma  considerably  undercooled,  to  be  approached  at 
all  within  a  limited  time.  By  way  of  illustration  note  the  percentage  of  glass 
revealed  by  the  microscopic  study  of  the  Lassen  Peak  rocks  (p.  43).  This  glass  is 
undercooled  magma  in  continuous  and  intimate  contact  with  the  crystalline  phases 
throughout  the  mass.  When  Morey  considers  the  case  of  an  undercooled  magma  at 
700°  or  8oo°  to  be  radically  altered  by  the  advent  of  water  vapor,  he  pictures 
phenomena  of  common  occurrence  in  the  study  of  rocks  of  high  silica  content. 
Such  an  andesite  magma  containing  several  per  cent  of  water  may  be  in  intimate 


Fig.  42. — May  22,  1913.  View  of  the  great  eruption  from  Red  Bluff, 

45  miles  southwest.  Photo  Stinson. 

contact  with  the  crystalline  phases  at  these  temperatures  and  yet  be  very  far  re¬ 
moved  from  equilibrium.  Undercooling  might  indeed  be  accounted  to  be  the 
normal  condition  of  such  a  system  when  inclosed  within  a  competent  reservoir,  and 
inertness  its  most  apparent  characteristic. 

Suppose  additional  water  vapor  under  appropriate  pressure  to  be  introduced 
into  such  a  system.  The  solubility  for  water  of  the  liquid  portion  (magma)  is 
greater  at  these  low  temperatures  and  increased  fluidity  of  the  magma  is  its  im¬ 
mediate  consequence.  But  with  increased  fluidity  comes  an  increased  reaction- 
rate,  a  more  rapid  approach  toward  equilibrium  through  crystallization,  to  which 
may  correspond  an  enormous  increase  in  the  vapor  tension  (see  curve,  p.  78).  In  a 
volcano  reservoir,  with  vast  quantities  of  surcharged  magma  potentially  available, 
such  a  discharge  of  water  vapor  may  precipitate  an  avalanche  of  crystallization 
and  consequences  of  catastrophic  proportions. 

If  this  reasoning  is  admitted,  no  natural  agency  need  be  invoked  to  explain 
this  type  of  volcanism,  which  does  not  find  its  place  among  the  well-established 


84 


laws  of  the  behavior  of  solutions.  Ultraviscosity  may  provide  a  cloak  beneath  which 
slow-moving  changes  may  proceed  unobserved  for  long  periods  of  time,  and  these 
may  develop  a  potential  of  enormous  proportions  before  conditions  favorable  to  its 
discharge  (equilibrium)  occur,  but  there  appears  to  be  nothing  in  this  special  case, 
except  its  magnitudes,  which  is  in  any  way  foreign  to  our  usual  thinking,  and  these 
will  give  us  no  concern,  provided  only  we  have  the  courage  to  follow  the  reasoning 
through  to  the  logical  outcome. 

After  establishing  the  validity  of  such  reasoning  we  shall  not  overlook  the 
facts,  nor  set  them  aside  as  mere  coincidence,  that  (i)  streams  of  water  from  the 
melting  snow  in  the  crater  basin  were  observed  to  be  pouring  into  the  first  explosion 
crater  and  adjacent  cracks  at  the  beginning  of  the  activity  in  May  1914;  (2)  a  very 
unusual  winter  accumulation  of  snow  in  the  crater  preceded  the  culminating 
outbreak  in  May  1915;  (3)  following  the  great  eruption  in  1915  and  the  upheaval  of 
the  crater  floor  which  formed  a  part  of  it,  the  rocks  in  the  crater  remained  warm 
throughout  the  winter  following  and  were  found  to  be  quite  bare  of  snow  in  May 
1916 — whether  from  lack  of  a  new  supply  of  water  to  diminish  the  viscosity  and  so 
to  give  fresh  impulse  to  the  crystallization,  or  for  some  other  reason,  there  were  no 
eruptions  in  May  1916  or  thereafter  in  that  season;  (4)  after  the  surface  rocks  at  the 
summit  had  cooled  and  the  winter  snows  again  accumulated  there  (1916-17),  the 
period  of  spring  melting  (May  1917)  was  again  marked  by  violent  explosions  which 
opened  a  new  explosion  crater  some  600  feet  wide  and  deep. 

Since  the  summer  of  1917  the  opening  has  remained  sealed,  so  far  as  trust¬ 
worthy  observations  at  the  summit  have  been  reported. 

When  the  remarkably  low  temperature  of  all  the  observed  phenomena  is 
recognized  and  the  consequent  high  viscosity  which  characterized  the  only  lava 
movement  observed  during  the  entire  eruptive  cycle,  it  is  hardly  possible  to  con¬ 
clude  that  the  volcano  hearth  itself  can  have  had  a  high  temperature.  If  it  had  not, 
then  undercooling  and  an  extremely  slow  rate  of  crystallization  is  indicated,  which 
may  have  required  an  influx  of  surface  water  to  precipitate  violent  phenomena. 


PART  II. 

THE  HOT  SPRINGS  OF  LASSEN 
NATIONAL  PARK 


By  Arthur  L.  Day  and  E.  T.  Allen. 


85 


INTRODUCTION. 


In  the  course  of  the  investigation  of  the  recent  eruption  at  Lassen  Peak  some 
interesting  observations  were  made  in  1915  on  the  hot  springs  of  that  vicinity. 
The  possibility  of  studying  certain  genetic  conditions  for  the  formation  of  sulphide 
minerals  was  suggested  by  what  appeared  to  be  the  precipitation  of  pyrite  in  one  of 
the  hot-spring  areas.  The  next  year  observations  were  continued  with  this  purpose 
in  view,  and  collections  were  brought  home  for  laboratory  study.  As  the  investiga¬ 
tion  developed,  the  original  purpose  broadened  in  scope,  and  when,  after  the 
interruption  of  the  war,  the  work  was  taken  up  again  the  reed  of  more  complete 
evidence  on  a  number  of  points  became  obvious.  Accordingly,  the  field  was 
revisited  in  1922  and  again  in  1923. 


CHAPTER  I. 

OBSERVATIONS  AND  EXPERIMENTAL  WORK. 

LOCATION  OF  SPRINGS. 

The  hot  springs  described  in  this  paper  are  found  in  northeastern  California. 
They  occupy  adjacent  portions  of  Plumas,  Shasta,  and  Tehama  Counties  and,  with 
the  single  exception  of  Morgan’s  Springs,  all  are  included  within  the  limits  of  the 
Lassen  National  Park.  This  region,  which  has  but  recently  (1916)  been  established 
a  national  park,  is  comparatively  little  known,  because  it  lies  remote  from  the  main 
lines  of  travel  and  is  still  traversed  only  by  rough  trails,  but  it  abounds  in  attractions 
both  for  the  scientist  and  nature  lover— magnificent  scenery  of  mountain,  meadow, 
lake,  and  stream,  a  wonderful  forest  of  great  conifers,  and  volcanic  phenomena  of 
high  interest,  including  Lassen  Peak  and  many  groups  of  hot  springs. 

GEOLOGIC  RELATIONS  OF  HOT  SPRINGS. 

The  region  about  Lassen  Peak  is  covered  by  thick  lava  flows,  almost  exclusively 
dacite  and  andesite.  There  is  a  small  area  of  basalt  along  the  west  side  of  Bumpass 
Hell,  as  one  of  the  largest  hot-spring  areas  is  called,  but  elsewhere  the  dacite  is 
uppermost.  At  the  Devil’s  Kitchen  this  reaches  an  estimated  thickness  of  1,200 
feet.  Below  it  lies  an  andesite  flow  of  unknown  thickness.  The  hot  springs  all 
occur  in  the  dacite  areas. 

A  more  significant  relation  is  the  association  of  the  springs  with  a  system  of 
faults.1  According  to  Mr.  J.  S.  Diller,  of  the  U.  S.  Geological  Survey,  to  whom 
we  are  indebted  for  these  geological  observations,  there  exists  between  the  Sierra 
Nevada  and  the  Klamath  Mountains  “a  group  of  features,  mainly  faults”  which 
parallel  the  Lassen  volcanic  ridge.  It  is  in  this  structural  belt  “which  has  aligned 
the  volcanoes”  that  all  the  hot  springs  of  the  region  occur.  The  faults  are  gen- 
really,  if  not  always,  normal  faults.  As  we  approach  the  Sierra  these  faults 
penetrate  to  shallower  depths  and  hot  springs  are  no  longer  found. 

HOT-SPRING  GROUPS. 

There  are  at  least  eight  groups  of  hot  springs  in  the  Lassen  region,  occurring  at 
intervals  of  a  few  miles.  Their  alignment,  as  Mr.  Diller  points  out,  suggests  that 
they  follow  two  intersecting  fissures;  the  Geyser,  Boiling  Lake,  Drake’s  Springs, 
Devil’s  Kitchen,  and  Bumpass  Hell  on  the  one;  Mill  Creek  Springs,  Supan’s 
Springs,  and  Morgan’s  Springs  on  the  other.  Our  observations  included  all  but 
the  last  group,  but  most  of  the  work  was  done  on  the  Boiling  Lake,  Devil’s  Kitchen, 
and  Bumpass  Hell.  So  far  as  the  different  groups  have  been  studied  their  essential 
characteristics  are  the  same. 

1  Bunsen  ( Liebig’s  Annalen,  62,  1,  1847)  points  out  that  practically  all  the  springs,  geysers,  and  fumaroles  of  Iceland 
lie  along  a  northeast-southwest  line,  without  regard  to  mountains  or  valleys. 

87 


88 


Geyser. 

The  Geyser  is  the  name  applied  to  the  principal  spring  of  a  small  group 
which  occurs  in  a  deep,  narrow  ravine  about  io  miles  southeast  ol  Lassen  Peak, 
Like  each  of  the  three  following  spring  groups,  it  is  situated  in  Plumas  County, 
California.  Ranged  in  an  irregular  line  at  the  head  of  the  ravine  are  three 
connecting  pools,  each  about  25  feet  in  diameter,  the  Geyser  itself  being  first  in 
order.  The  ravine  at  this  point  is  but  little  wider  than  the  Geyser  pool.  The 
temperature  of  the  pools  varies  from  20°  or  30°  up  to  nearly  boiling  temperature, 
which  at  this  elevation  (5,700  feet  by  the  aneroid)  is  not  far  from  940  C.  Two  of 
the  pools  have  been  observed  at  times  to  spout  jets  of  water  to  a  height  of  5  to  8 


Fig.  43. — The  Geyser.  Southernmost  pool,  July,  1922.  Photo  Day. 


feet,  at  other  times  the  action  is  inconsiderable  (fig.  43,  Plate  7).  A  small  cold 
stream  flows  down  into  the  ravine  in  the  spring  of  the  year,  but  dries  up  in  late 
summer.  Along  the  little  stream,  which  drains  the  hot  pools,  thermal  activity 
continues  for  a  short  distance  in  the  form  of  insignificant  fumaroles.  From  a  point 
at  the  top  of  the  ravine  a  narrow  lava  flow,  like  a  windrow  in  form,  can  be  followed 
northwestward  almost  to  the  Boiling  Lake. 

Boiling  Lake  or  Lake  Tartarus. 

The  Boiling  Lake  (elevation  5,750  feet)  is  an  oval  basin  of  hot  water,  200  yards 
in  its  largest  diameter,  set  in  a  beautiful  evergreen  forest,  7  or  8  miles  southeast  of 
Lassen  Peak  (figs.  44,  45,  Plate  8).  Except  at  the  lower  (northwest)  end,  its  banks 
are  steep  and  from  15  to  75  feet  in  height.  The  basin-like  form  of  the  depression 
and  the  associated  thermal  phenomena  suggest  the  site  of  an  ancient  crater  (Diller). 
There  is  a  very  small  cold  stream  flowing  into  the  lake  from  the  south  and  an  outlet 
of  warm  water,  slightly  larger,  at  the  northern  end.  During  the  summer  both  dry 


PLATE  7 


■ 


The  Geyser.  Northernmost  Pool.  (1)  June,  1916,  Temperature  30°,  No 
spouting.  (2)  June,  1 91  3,  Temperature  93°.  (3)  July  1 922,  Temperature  94°. 

Photo  Day. 


J 


1 

Of  JHt 


V 


89 


up  completely  (fig.  44).  Gas  bubbles  rise  from  time  to  time  at  various  points  on 
the  surface.  In  spring  and  summer  the  temperature  averages  about  50°  C.;  our 
observations  varied  from  46°  to  520.  The  lake  is  pale  green  in  color  and  choked 
with  a  fine  cream-colored  mud  which  makes  it  appear  quite  shallow.  Cling¬ 
ing  to  the  muddy  bottom  of  the  outlet,  and  occasionally  in  slight  amounts  to  the 
earth  about  the  borders  of  the  springs,  is  found  a  green  growth  which  in  all  prob¬ 
ability  consists  of  algae,  to  which  the  greenish  color  of  the  lake  is  perhaps  due. 
Algae  were  not  noticed  in  the  other  hot-spring  areas,  except  in  Drake’s  Springs; 
if  present  at  all  they  must  be  scarce. 


The  lake  is  almost  completely  encircled  by  a  chain  of  small  springs  and  mud 
pots,  most  of  which  are  near  the  boiling  temperature.  They  generally  occur  close 
to  the  shore.  Some  are  found  on  the  bank  up  to  30  feet  above  the  water,  some  are 
spread  out  over  a  low-lying  delta  at  the  inlet,  and  some  of  the  mud  pots  are  sub¬ 
merged  or  surrounded  by  the  lake  at  high  water  (fig.  46,  Plate  9). 


Fig.  44. — July  23,  191  3.  Boiling  Lake  (Temp.  50°  C)  surrounded  by  a  beautiful  evergreen 
forest.  Outlet  (then  dry)  in  the  foreground.  Pyrite  crystals  abundant  in 
the  bed  of  the  stream.  Photo  Day. 


90 


As  a  result  of  the  action  of  thermal  waters,  the  shores  of  the  lake  tor  a  maximum 
distance  of  some  50  yards  at  the  northwestern  end  are  of  bare  earth — a  thoroughly 
decomposed  lava  colored  reddish  by  oxide  of  iron. 


Fig.  45. — May  19,  1916.  Boiling  Lake  looking  northwest.  Lassen  Peak  in  the  back¬ 
ground.  Photo  Day. 

Drake’s  Springs. 

Three-quarters  of  a  mile  north  of  Boilirg  Lake  in  the  close  vicinity  of  Warner 
Creek  is  a  small  group  of  springs  (elevation,  5,500  feet)  which  differ  in  appearance 
from  all  others  in  the  region.  As  a  consequence  of  the  lower  temperatures  and 
probably  also  other  conditions  prevailing  here,  the  waters  are  choked  with  a  bright- 
green  vegetable  growth,  contrasting  strongly  with  the  barrenness  of  the  other  spring 
areas.  The  highest  temperature  we  have  observed  at  any  time  in  these  springs  is 
62°  C.  Besides  a  number  of  seepages,  theie  are  a  very  few  well-marked  springs, 
all  quite  small  and  practically  all  on  the  slope  which  runs  down  to  the  south  bank 
of  Warner  Creek.  The  easternmost  spring  is  the  largest  and  hottest. 

The  mineral  content  of  Drake’s  Springs  is  of  similar  character  to  that  of  all 
the  rest,  so  far  as  the  salts  are  concerned,  but  they  are  small  in  quantity  and  there 


PLATE  8 


May  19,  1916.  Boiling^  Lake.  The  outlet  at  high  water. 


tut  littMM 


91 


is  no  free  acid  and  apparently  no  hydrogen  sulphide.  These  qualities  adapt  the 
waters  to  bathing  purposes,  and  chiefly  for  this  reason  a  summer  camp  has  been 
located  here  for  several  decades.  The  camp,  which  belongs  to  Mr.  A.  Sifford,  has 
always  been  our  stopping-place,  as  it  forms  the  most  convenient  base  for  all  points 
of  interest  in  the  Lassen  region. 


Fig.  46. — May  26,  1916.  Springs  on  the  bank  of  Boiling  Lake.  Pyrite  crystals  abundant 
in  the  clay  banks.  Photo  Day. 

Devil’s  Kitchen. 


The  site  of  the  Devil’s  Kitchen  (elevation  about  5,800  feet)  is  a  deep,  narrow 
valley  through  which  flows  a  swift,  cold  stream  about  15  feet  in  width  and  1  or  2 
feet  deep,  called  Warner  Creek.  The  active  area,  which  is  approximately  550 
feet  by  1,300  feet  in  extent,  is  about  1.5  miles  west  of  Drake’s  Springs  and  6  miles 
southeast  of  Lassen  Peak.  The  south  wall  of  the  Kitchen  is  precipitous  and  several 
hundred  feet  in  height.  There  are  also  high  banks  on  the  north  side  of  Warner 
Creek  below  No.  27  (see  map  fig.  47)  and  at  either  end  of  the  area.  On  these 
steep  slopes  there  is  almost  no  sign  of  thermal  activity,  but  many  mud  pots  and  hot 
springs  are  scattered  over  the  irregular  floor  of  the  Kitchen.  In  the  immediate 
vicinity  of  the  springs  the  ground  is  practically  always  bare  of  vegetation,  but  pines, 


92 


Fig.  47—  Sketch  Map  of  “Devil’s  Kitchen”  area,  six  miles  southeast  of  Lassen  Peak.  Numbered  and  lettered  springs  referred  to  in  the  text. 


PLATE  9 


May  19,  1916.  Mud  pots  on  the  shore  of  the  Boiling  Lake  (high  water).  Photo  Day. 


IHt  uttfURl 
^  Of  THfc 


93 


cedars,  etc.,  are  distributed  over  the  area  wherever  conditions  are  favorable,  and 
north  of  the  creek  beyond  a  barren  border  strip  the  ground  is  forested.  Thermal 
activity  reaches  its  greatest  intensity  at  the  two  ends  of  the  area,  especially  the 
eastern,  where  there  are  several  strongly  spouting  springs  and  well-marked  fuma- 
roles  (figs.  48  and  73).  The  temperatures  are  no  higher  than  at  the  Boiling  Lake, 
but  the  thermal  activity  as  measured  by  the  volume  of  hot  water  is  considerably 
greater. 


Fig.  48. — July  21,  1915.  Four  steaming  springs  at  the  foot  of  a  high  bank,  east  end  of 
Devil’s  Kitchen.  Warner  Creek  in  the  foreground.  Photo  Day. 


In  outward  aspects  there  are  other  differences  between  the  two  areas.  A 
number  of  pools  in  the  upper  end  of  the  Devil’s  Kitchen  are  colored  yellow  with 
precipitated  sulphur,  while  free  sulphur  is  hardly  noticeable  at  the  Boiling  Lake. 
There  are  also  pools  in  the  Devil’s  Kitchen  covered  by  a  dark  scum  which  has 
proved  to  be  pyrite.  In  the  flats  near  Warner  Creek  the  ground  has  been  reduced 
by  the  action  of  the  hot  waters  to  a  fine,  hot,  sticky  mud  which  dries  out  and  be¬ 
comes  baked  into  a  thin  crust,  through  which  one  may  easily  break  with  serious 
results  (Plate  10). 


94 


Bumpass  Hell. 

Bumpass  Hell,  2  miles  due  south  of  Lassen  Peak,  is  a  crater-shaped  basin  500 
by  1,400  feet  in  area,  lying  high  up  among  the  mountains  (elevation  about  8,000 
feet)  and  almost  absolutely  devoid  of  vegetation  (figs.  49,  55,  Plate  11).  Quite  the 
most  picturesque  of  any  of  the  hot-spring  areas,  its  barren  ground,  sulphur  caul¬ 
drons,  boiling  fountains,  and  disagreeable  odors  form  a  striking  contrast  to  the 
wooded  slopes  by  which  the  traveler  approaches  it  and  the  magnificent  mountain 
scenery  visible  from  the  rim  of  the  basin.  Thermal  action  here,  if  not  more  intense 
than  in  the  other  areas,  has  been  at  least  decidedly  concentrated.  Rock  decom- 


Fig.  49. — View  of  Bumpass  Hell  (looking  west)  taken  in  1891.  Activity 
greater  than  at  the  present  time.  Photo  E.  R.  Drew. 


position  at  the  surface  is  thorough.  It  not  only  covers  the  ground  of  the  entire 
basin,  but  extends  to  adjacent  peaks  and  slopes.  Thus  the  long,  steep  slope,  which 
is  traversed  by  the  little  stream  forming  the  outlet  of  the  basin,  has  been  similarly 
decomposed  for  a  distance  of  several  hundred  yards  and  many  small  fumaroles  and 
springs  of  high  temperature  are  still  active  there.  The  surface  of  the  slope  which 
rises  to  the  southeast  of  Bumpass  Hell,  the  steepness  of  which  is  indicated  on  the 
map  (fig.  50),  has  also  been  similarly  transformed.  A  glance  at  the  map  shows  that 
the  eastern  portion  of  the  floor  of  the  basin  is  quite  irregular,  rising  in  barren  mounds 
among  the  pools  (fig.  55).  The  ground  of  Bumpass  Hell,  more  especially  the  west¬ 
ern  part,  is  undermined,  sounds  hollow  to  the  tread,  and  is  easily  broken  through. 
One  of  the  most  conspicuous  features  of  this  area  is  the  large  size  and  the  compara¬ 
tively  small  number  of  the  pools.  Another  characteristic  is  the  prevalence  of  free 
sulphur,  which  occurs  as  a  precipitate  in  some  of  the  pools  (figs.  52,  61,  62),  and 
which,  in  the  form  of  needles,  lines  many  small  fumaroles  on  the  western  side. 
Mud  pots  are  found  in  considerable  number,  but  not  so  many  as  in  the  Devil’s 
Kitchen.  One  of  them  on  the  north  side  (No.  17,  fig.  50;  fig.  77)  is  conspicuous 
for  its  size,  about  20  feet  in  diameter. 


PLATE  10 


Of  IHt 

w&wi  m  kirnis 


95 


IQO _ ZOO _ 300 _ 450 _ Spo  FEET 

Contour  interval  6  ffeet.  (Approximate) 

Ete  vat/ on  approximately  6000  feet _ 

Fig.  50. 


:"W 


96 


Temperatures  at  Bumpass  Hell  usually  approach  the  temperature  of  boiling 
water  for  that  elevation,  91 0  to  920,  but  one  vigorous  roaring  fumarole  (No.  8, 
fig.  50)  showed  in  1916  a  maximum  temperature  of  1 1 7. 50  C.,  and  in  1923  was  still 
considerably  above  the  temperature  of  boiling  water. 

Rising  above  the  northeastern  rim  of  the  basin  is  a  lava  flow  that  forms  a  con¬ 
siderable  ridge  which  can  be  followed  by  the  eye  for  some  distance  as  one  approaches 
Bumpass  Hell  by  the  usual  trail  along  King’s  Creek. 


Fig.  51. — July  10,  1915.  Large  shallow  pool,  bright  brown  color,  considerable  gas  evo¬ 
lution  (center),  pyrite  scum  (right).  Photo  Day. 


Supan’s  Springs. 

In  the  nearly  straight  line  from  Boiling  Lake,  Devil’s  Kitchen,  and  Bumpass 
Hell  is  another  small  hot-spring  area  in  Mill  Creek  Valley,  known  locally  as  Supan’s 
Springs.  It  lies  nearly  3  miles  to  the  west  of  Bumpass  Hell  and  about  4  miles 
southwest  of  Lassen  Peak.  The  surrounding  topography  suggests  that  it  may 
represent  a  residual  trace  of  the  great  crater  basin  which  preceded  Lassen  Peak, 
of  which  Brokeoff  Mountain  is  the  most  conspicuous  remnant.  In  appearance 
Supan’s  Springs  resemble  most  closely  those  of  the  Devil’s  Kitchen.  They  include 
small  mud  pots  and  a  number  of  small  springs,  some  turbid  and  some  clear,  as  in 


warn 


PLATE  11 


Plate  11 — July  10,  1915.  A  portion  of  Bumpass  Hell  looking  southwest.  Photo  Day. 


!f 


-tv 


97 


the  case  of  the  Devil’s  Kitchen,  but  the  drainage  basin  is  much  smaller  and  the 
stream  which  flows  through  the  valley  is  insignificant.  This  is  perhaps  partly  due 
to  the  very  steep  grades,  which  carry  away  the  water  much  more  rapidly  than  in 
any  of  the  basins  heretofore  described. 

The  temperatures  are  substantially  identical  with  those  found  in  Bumpass 
Hell,  the  maximum  (91. 6°)  being  equivalent  to  the  boiling  temperature  of  water 
corresponding  to  the  elevation.  The  soil  is  much  decomposed  (fig.  53),  the  ac- 


Fig.  52  July  10,  1915.  Large  sulphur  cauldron  (No.  4;  fig.  50),  Bumpass  Hell.  No  outflow. 

Little  gas.  Photo  Day. 


cumulations  of  sulphates  being  greater  in  this  valley  than  in  any  other  part  of  the 
region.  Formerly  considerable  deposits  of  pure  sulphur  existed  here,  but  in  so  far 
as  they  were  exposed  to  plain  view  they  have  been  carried  away  in  sporadic  mining 
operations.  There  are  no  surface  evidences  of  large  deposits  and  presumably  the 
region  would  not  repay  commercial  exploration  for  sulphur. 

Some  200  yards  above  this  group  of  springs  is  a  spring  somewhat  larger  than 
any  of  the  others,  to  which  is  sometimes  given  the  name  Upper  Supan’s  Spring. 
The  hillside  is  so  steep  at  this  point  that  the  action  of  the  spring  has  produced  a 
slight  embayment  of  the  hillside  so  as  partially  to  roof  over  the  active  basin.  The 
basin  itself  is  about  6  feet  in  diameter  and  contained  no  more  than  4  or  5  inches  of 


98 


water  in  August  1923.  This  pool  was  slightly  turbid,  gray  in  color,  and  was 
boiling  quite  violently  over  the  entire  surface,  which  was  probably  caused  entirely 
by  the  escape  of  steam  through  it.  There  was  no  indication  of  other  gases  and  no 
samples  were  taken. 

If  one  follows  up  the  valley  from  Supan’s  Springs  directly  toward  Lassen  Peak 
one  may  notice  an  ancient  basin  in  which  are  only  2  or  3  small  springs,  slightly 
sulphur-colored  and  in  part  surrounded  by  vegetation  (fig.  54).  These  are  prob¬ 
ably  the  highest  springs  in  the  valley  which  feed  Mill  Creek,  and  so  perhaps  they 
might  be  called  its  source.  The  contours  of  the  basin  suggest  one  of  the  last 
centers  of  ancient  activity,  of  which  nothing  more  remains  than  these  feeble  hot 
springs.  There  is  little  of  interest  to  note  about  this  group  of  springs,  save  only 
that  they  are  north  of  the  line  upon  which  all  of  the  hot-spring  regions  thus  far 
described  are  located.  It  is  therefore  natural  to  conclude  that  they  are  not  con- 


Fig.  53. — July  1923.  Supan’s  Springs,  lower  group,  showing  the  effects 
of  thermal  action.  Photo  Day. 

nected  with  the  major  east-and-west  fault  of  the  region,  but  with  a  north  and  south 
fault  leading  to  the  extinct  center  of  former  volcanic  activity.  The  volume  of 
water  in  the  springs  themselves  is  negligibly  small,  the  largest  being  no  more  than 
2  or  3  feet  in  diameter  and  a  few  inches  deep,  the  exact  dimensions  being  partially 
concealed  by  small  boulders  and  vegetation.  It  should  be  said,  however,  that 
the  entire  basin,  even  in  August,  was  saturated  with  water,  indicating  that  the 
drainage  follows  small  seepages  without  being  localized  into  springs. 

Morgan’s  Springs. 

Morgan’s  Springs  were  not  visited  during  any  of  our  expeditions  to  Lassen 
Peak.  They  lie  several  miles  to  the  south  of  the  major  fault  to  which  our  studies 
were  directed,  and  at  a  much  lower  level  (on  Mill  Creek),  thus  indicating  to  us  that 
they  were  perhaps  not  closely  related  to  the  sources  of  the  volcanic  activity 


99 


which  it  was  our  chief  interest  to  study.  The  following  description,  taken  from 
Waring’s1  account  of  Morgan’s  Springs,  is  here  quoted,  in  order  to  complete  the 
account  of  the  known  hot  springs  of  the  region.  They  occupy  a  small  meadow 
which  forms  the  floor  of  a  narrow  valley  where  “about  25  springs  and  pools  are 
scattered  for  a  distance  of  600  yards  along  Mill  Creek.”  The  meadow  is  a  part  of 
Morgan’s  ranch. 

Most  of  the  springs  are  quiet  pools  of  small  flow,  less  than  5  feet  in  diameter  and  rela¬ 
tively  shallow.  A  number  of  them  contain  thick  algous  growths  and  several  deposit  native 
sulphur.  Others  rise  in  areas  where  hard  deposits  of  siliceous  and  calcareous  materials 
have  formed.  Three  or  four  springs  steam  and  sputter  from  vents  on  the  banks  of  the 
creek.  One  of  the  northernmost  of  these  springs  seems  to  have  a  true  geyser  action  for  it 
issues  in  a  shallow  basin  3  feet  in  diameter  in  which  water  is  said  to  come  to  a  state  of 
vigorous  ebullition  and  then  to  subside  about  once  a  day.  During  a  period  of  41  hours  the 


Fig.  54. — July  1923.  Mill  Creek  Hot  Springs.  Probably  the  last 
vestige  of  activity  in  the  old  Lassen  Peak  crater  southeast 
of  Brokeoff  Mountain.  Photo  Day. 

condition  of  this  spring  was  noted  five  times  as  follows:  At  the  beginning  of  the  period  in 
active  ebullition,  discharge  about  15  gallons  a  minute,  temperature  above  930  C.;  two  hours 
later  quiet,  no  overflow,  temperature  86°  C.;  at  16  hours  and  at  25  hours  later,  in  active 
ebullition,  overflowing;  at  41  hours  quietly  overflowing,  about  five  gallons  per  minute. 

Waring  says  that — 

The  siliceous  deposit  at  Morgan’s  springs  is  thought  to  be  the  largest  spring  deposit  of 
this  material  in  the  state.  .  .  .  The  slopes  on  each  side  of  the  meadow  are  covered  with 
pyroxene  andesite  of  Miocene  or  Pliocene  age,  but  a  cemented  conglomerate  is  exposed 
along  the  creek  in  the  meadow  where  the  springs  rise.  The  cementing  material  is  siliceous 
and  has  probably  been  deposited  by  the  hot  water. 

Some  of  the  above  features  obviously  differ  considerably  from  any  that  have 
been  observed  in  the  other  spring  areas.  The  waters  also,  so  far  as  they  have  been 


1  Springs  of  California,  U.  S.  Geol.  Survey,  Water  Supply  Paper  338,  p.  138,  1915. 


100 


examined,  are  exceptional  in  containing  a  preponderant  amount  of  chlorides  and 
in  their  high  concentration  (p.  no).  Waring  suggests  that  the  chlorine  may  be 
derived  from  the  sediments  of  the  Chico  formation,  outcrops  of  which  were  dis¬ 
covered  by  Diller  20  miles  to  the  west  and  southwest.  The  highest  recorded 
temperature  which  has  been  observed  in  Morgan’s  Springs  is  95.6°  (Diller). 
This  indicates  that  the  area  is  lower  than  any  of  the  other  hot-spring  basins  de¬ 
scribed  in  this  book. 


Fie.  55. —  July  10,  1915.  General  view  of  Bumpass  Hell  hot  springs,  looking  west. 

(Cf.  Fig.  49).  Photo  Day. 

Types  of  Springs. 


The  hot  springs  of  the  Lassen  region  are  chiefly  of  the  solfataric  type  and  are, 
so  far  as  one  may  depend  on  descriptions,  duplicated  in  many  parts  of  the 
world.  They  resemble  closely  the  acid  springs  in  the  Norris  Basin  of  the  Yellow¬ 
stone  Park.  At  first  sight  the  visitor  is  impressed  by  the  diversity  in  appearance 
which  the  springs  present.  In  size,  amount,  and  color  of  sediment,  and  in  physical 
activity  the  differences  are  in  fact  very  great.  Individual  spring  pools  range  in 
size  all  the  way  from  a  diameter  ol  50  feet  or  more  down  to  insignificant  dimensions. 
Though  they  have  never  been  gauged,  it  is  obvious  to  an  observer  that  the  dis¬ 
charge,  even  from  the  largest  springs,  is  quite  small,  and  some  have  no  visible  out¬ 
let  at  all. 

One  of  the  best-defined  types  and  perhaps  the  most  striking  is  the  spouting  or 
pulsating  spring.  The  pool  may  vary  greatly  in  size,  but  the  spring  is  character- 


101 


ized  by  one  or  more  jets  of  water  which  spurt  spasmodically  and,  with  considerable 
regularity  at  intervals  of  a  second  or  so,  to  a  height  varying  from  a  few  inches  to  5 
or  10  feet.  The  volume  of  the  fountain  also  varies  considerably.  Sometimes  it  is 
dome-shaped,  but  usually  it  is  like  a  jet  from  a  nozzle.  The  height  to  which  the 
same  fountain  may  play  differs  greatly  at  different  times  and  it  may  even  cease 
altogether  (Plate  7).  But  such  springs  are  not  to  be  regarded  as  geysers  of  irreg¬ 
ular  period,  as  they  are  not  characterized  by  eruptions  which  appear  and  disappear 
suddenly.  In  fact,  there  are  no  geysers  in  the  Lassen  region.  The  spouting  in 
these  springs  naturally  keeps  the  water  stirred  up  and  they  are  usually  muddy, 
though  an  outlet  of  sufficient  size  helps  to  keep  them  clear  of  sediment. 


Fig.  56. — July  10,  1915.  Large  mud  pot  in  Bumpass  Hell.  Inactive  since  1915.  Photo  Day. 


Mud  Pots  and  Mud  Volcanoes. 

The  essential  characteristics  of  a  mud  pot  seem  to  be  a  very  limited  water 
supply,  a  relatively  large  supply  of  heat,  and  the  lack  of  any  visible  outlet  (figs. 
56,  57,  58  and  Plate  9).  The  mud  it  contains  is  generally  thick  and  pasty,  though 
it  varies  considerably;  in  fact,  all  degrees  of  consistency  down  to  slightly  turbid 


1  With  the  possible  exception  of  the  single  spring  in  the  Morgan  group  described  above. 


102 


water,  are  found  in  the  various  springs.  Some  of  the  mud  in  the  mud  pots  is 
unquestionably  a  product  of  chemical  action  on  the  spot,  but  in  some  places  a  part 
of  the  mud  is  probably  transported.  Thus  all  about  the  Boiling  Lake  occur  mud 
pots  issuing  from  the  sediment  which  is  probably  transported  to  the  shores  at  high 


Fig.  57. — June,  1922.  Mud  pot  in  the  Devil’s  Kitchen 
(No.  1  0,  Fig.  47).  Bursting  gas  bubble  in  the 
foreground.  Very  thick  mud.  Photo  Day. 


Fig.  58. — July,  1923.  Boiling  Lake,  Mud  pot  active  below  the  lake  level 
(foreground),  others  drowned.  Very  low  water.  Photo  Day. 

water.  Some  of  this  was  probably  formed  by  thermal  action  at  various  points  on 
the  lake  bottom,  and  some  has  been  carried  into  the  lake  through  the  outlets  of 
other  hot  springs. 


103 


A  mud  volcano  differs  from  a  mud  pot  much  as  a  spouting  spring  differs  from  a 
quiet  hot  spring.  When  the  water  of  a  mud  pot  dries  out  sufficiently  the  escaping 
steam  throws  out  clods  of  mud,  which  in  falling  build  up  a  cone  inclosing  a  crater 
just  as  spouting  lava  does.  The  pressure  of  the  steam  must  obviously  be  equal  to 
the  work  required.  Thus  a  very  large  and  rather  active  mud  pot  in  the  Devil’s 
Kitchen  (No.  io,  fig.  47;  fig.  57)  has  never  within  the  time  of  our  observation  built  up 
walls  of  any  considerable  height  because,  though  the  mud  is  constantly  spluttering, 
the  pot  is  unusually  deep  and  wide,  while  the  steam  pressure  is  not  proportionately 
great.  The  result  is  that  most  of  the  mud  drops  back  into  the  pot  and  compar¬ 
atively  little  falls  on  the  rim  (fig.  58).  In  consequence  of  a  wet  season,  a  mud 
volcano  sometimes  slumps  in,  forming  a  mud  pot  again,  for  mud  pots  have  been 
found  at  points  where  in  drier  times  mud  volcanoes  had  been  observed.  In  1916 
a  number  of  mud  volcanoes  were  to  be  seen  both  at  the  Boiling  Lake  and  the 
Devil’s  Kitchen;  in  June  1922  all  had  disappeared  and  their  sites  were  occupied  by 
mud  pots.  In  August  1923  all  these  and  many  other  smaller  ones  had  once  more 
built  up  mud  cones. 

These  three  forms,  spouting  springs,  mud  pots,  and  mud  volcanoes,  are  the 
most  distinctive  types  of  hot  springs  which  we  have  to  consider.  The  differences  in 
the  color  of  the  spring  sediments  are  also  of  a  striking  character,  but  when  we  come 
to  the  study  of  the  chemical  nature  of  the  sediments  and  the  physical  character  of 
the  thermal  activity  we  shall  find  that  all  this  manifold  diversity  is  but  the  manifest¬ 
ation  of  the  same  process  due  to  the  same  fundamental  forces,  modified  here  and 
there  by  local  influences  most  of  which  are  of  secondary  importance. 


CHAPTER  II. 

FIELD  AND  LABORATORY  WORK. 

WORK  IN  THE  FIELD. 

The  field  work  included  detailed  observations  of  the  springs  and  their  relation¬ 
ships,  the  preparation  of  maps  of  the  three  most  important  spring  areas,  measure¬ 
ments  of  temperature  in  the  springs  and  of  ground  temperatures  in  some  areas, 
approximate  measurements  of  heat  carried  away  from  one  of  the  basins  by  out¬ 
flowing  water,  and  the  collection  of  waters,  salts,  sediments,  and  gases  for  laboratory 
study. 

Maps. 

Local  outline  maps  (i  inch  to  ioo  feet)  of  Lake  Tartarus  (fig.  59),  the  Devil’s 
Kitchen  (fig.  47),  and  Bumpass  Hell  (fig.  50),  were  made  for  the  purpose  of  indicat¬ 
ing  the  location  and  the  relation  of  the  springs  studied  and  providing  possible 
identification  which  might  permit  of  further  study.  It  must  be  recognized,  of 
course,  that  these  springs  are  situated  in  a  region  of  very  active  and  very  variable 
surface  drainage,  partly  due  to  the  heavy  accumulation  of  winter  snow,  and  also 
one  in  which  the  temperature  is  high  enough  to  bring  about  active  metamorphic 
changes,  so  that  shifting  in  the  observed  locations  of  springs  and  occasionally 
complete  loss  of  identity  may  be  expected. 

Our  observations  in  1922,  six  years  after  two  of  the  maps  were  prepared,  proved 
them  to  be  of  great  help  in  carrying  out  the  investigation.  Essential  changes  in 
that  time  had  been  comparatively  few,  but  some  there  were  which  were  incontest¬ 
able  and  of  special  interest.  The  areas  mapped  were  roughly  surveyed  with  a 
compass  and  all  distances  were  measured.  The  maps  are  therefore  to  scale. 
Letters  on  the  maps  refer  to  points  observed  by  J.  S.  Diller  in  1921,  the  numbers  to 
points  studied  by  the  authors. 

Temperature  Measurements. 

Temperature  measurements  were  made  with  a  maximum  mercurial  ther¬ 
mometer  protected  by  a  brass  cage.  As  there  was  no  reason  for  high  accuracy  it 
is  unnecessary  to  give  details.  The  results  are  recorded  in  Table  1. 

The  highest  temperatures  in  each  area  are  close  to  the  temperature  of  boiling- 
water  for  the  elevation.  They  are  usually  a  little  lower — a  fact  which  presumably 
means  that  the  influence  ol  escaping  gases  on  the  temperature  is  greater  than  that 
of  dissolved  salts.  The  temperature  fluctuations  in  some’  springs  are  much  too 
great  to  be  accounted  for  by  variations  in  the  barometer.  It  will  be  noted  also 
that  there  are  some  springs  and  pools  with  a  temperature  much  below  that  of 
boiling  water  and  rarely  a  cold  pool.  Eumarole  temperatures,  with  a  single  excep¬ 
tion  (Bumpass  Hell,  No.  8),  were  practically  the  same  as  the  maximum  temperatures 
found  in  the  springs. 


104 


105 


Table  i. — Temperatures  in  the  Hot  Springs  of  the  Lassen  National  Park.1 

The  Geyser. 


[Elevation  about  5.700  feet.  Average  boiling-point  of  pure  water  for  this  elevation  about  94.0°  C.] 


Locality. 

Date. 

Temp. 

Locality. 

Date. 

I 

Temp. 

North  pool . 

Do  . 

May  17,1916 
July  11,1915 
June  25,1922 

Aug.  9,1923 
May  17,1916 

. Do . 

°  C. 
32.8 
94.3 

92 

95.5 

37.2 

23.1 

93 

93.7 

Small  fumaroles  west  side  of  outflow.  . . 
Do . 

May  17 , 1916 
.  .  .  Do. 

°  C. 
89.3 
89.7 

8 

44 

.... 

Do . 

Do.  (boiling  steadily  3  to  5  feet 
high) . 

Cold  inflow  from  north: 

At  top  of  ravine . 

Near  bottom  of  ravine . 

June  25 , 1922 
....  Do .  . 

Middle  pool . 

Southwest  pool . 

Both  dry . 

Aug.  9,1923 

Do.  .' . 

Do.  (spouting  occasionally  10  feet). 

June  25,1922 
Aug.  9,1923 

The  Boiling  Lake 

or  I,ake  Tartarus. 

[Elevation  5,750  feet.  Average  boiling-point  of  pure  water  for  this  elevation  about  94.0° 

c.j 

Locality. 

Date. 

4  emp. 

locality. 

Date. 

Temp. 

°  C. 

°  C. 

Outlet  of  lake;  water  turbid . 

May  15,1916 

49 

No.  5.  Different  orifices . 

June  16,1922 

82.5  to  91 

Do . 

May  19,1916 

49 

Do . 

June  30, 1922 

85  5  to  94 

Do . 

May  26 , 1916 

50.8 

Do.  (muddy) . 

Aug.  9,1923 

90  0 

Do . 

June  8 , 1916 

49  0 

No.  6.  Mud  volcano . 

May  19 , 1916 

82 

Do . 

I  line  15 , 1922 

46.0 

Do . 

June  16, 1922 

80.5  to  90 

Do . 

July  9,1922 

52.5 

Do . 

June  19, 1922 

87.7,  91.5 

Do.  dry.  (Lake  temperature  near 

Do . 

July  9,1922 

93.5 

outlet) . 

Aug.  9,1923 

51.8 

Do.  (mud  clods,  banana  size, 

Muddy  pool  heated  by  spouting  springs: 

thrown  10  feet) . 

Aug.  9,1923 

86.3 

No.  1,  by  fallen  tree . 

May  26, 1916 

92 

Two  mud  pots  west  of  No.  6 . 

Tune  16,1922 

70  and  92 

Do . 

June  8,1916 

90.5 

Do.  (active  2  feet  below  lake  level). 

Aug.  9,1923 

92.9 

Do . 

June  30,1922 

93.5 

No.  7.  Mud  volcano . 

May  19,1916 

93 

Do . 

June  17,1922 

92 

Do . 

May  26, 1916 

90 

Do . 

July  9,1922 

93  8 

Do . 

June  8,1916 

93.9 

Do.  (much  enlarged) . 

Aug.  9, 1923 

93  3 

Do . 

June  15,1922 

90 

No.  1 ,  south  end . 

June  17,1922 

93 

Do . 

June  30,1922 

93 

Do .  . 

June  30 ’ 1922 

94.5 

Do . 

July  9,1922 

92 

Do . 

July  9,1922 

94.5 

Do . 

Aug.  9,1923 

93.3 

No.  2.  Very  small . 

May  15,1916 

91 

No.  8.  Lake  border . 

June  17 , 1922 

93 

Do.  .' . 

May  19 , 1916 

91  7 

Do . 

July  9,1922 

93.2 

Do . 

June  8 ’ 1916 

93 

Do.  (many  steam  openings;  little 

No.  2  (?) . . 

J  une  19 , 1922 

93 

water) . 

Aug.  9,1923 

89.9 

Do . 

July  9,1922 

94  2 

No.  8.  On  promontory  above  lake . 

June  17 , 1922 

92 . 7  to  94 

Do.  (very  low;  3  openings) . 

Aug.  9,1923 

93.4 

Do.  .' . ' . 

July  9^ 1922 

94 

No.  3.  Very  small . 

June  8 , 1916 

92  3 

No.  9.  Mud  pot  in  lake . 

June  30,1922 

93 

Do.  . 

May  19,1916 

89.7 

Do. . . ‘ . 

July  9,1922 

93 

No.  3  (?) . 

July  9,1922 

88 

Do.  (drv;  steam  onlv) . 

Aug.  9,1923 

Do.  banks  caved  in . 

Aug.  9,1923 

90.1 

No.  10. ....  . . . 

June  16,1922 

89  to  94 

No.  4.  Spouting  spring . 

May  15,1916 

93.2 

Do . 

June  30, 1922 

92  max. 

Do . 

May  19, 1916 

87 

I9o.  only  2  inches  deep;  scattering 

Do . 

June  16, 1922 

93.3 

bubbles . 

Aug.  9,1923 

90.8 

Do.  steam  only;  no  water . 

Aug.  9, 1923 

No.  1 1 . 

June  16,1922 

83 

No.  5.  Mud  springs . 

May  15 , 1916 

88 

Do.  3  steam  openings;  no  water...  . 

Aug.  9,1923 

94.8 

Do . 

May  19,1916 

80 

Do . 

June  8,1916 

89.2 

1  The  variation  in  the  observed  barometric  pressure  at  a  nearby  station  of  the  U.  S.  Weather  Bureau  was  12.7  mm.  during  the  period  of  our 
first  visit  (1916).  This  would  cause  a  variation  of  about  0.6°  C.  in  the  boiling-point  of  water. 


106 


Table  i. — Continued. 

Drake’s  Springs. 


[Elevation  about  5,500  feet.  Average  boiling-point  of  pure  water  for  this  elevation  about  94.0°  C.] 


Locality. 

Date. 

Temp. 

Locality. 

Date. 

Temp. 

°  C. 

°  C. 

Few  steps  NE.  of  bath  house . 

July  14,1922 

52 

Slope  south  of  Warner  Creek: — Continued 

Slope  south  of  Warner  Creek: 

Between  last  two,  but  nearer  bath- 

July  5,1915 

51.5 

bouse . 

July  14,  1922 

43  0 

Do . 

July  9,1915 

53 

Soda-spring,  effervescent,  0.75  mile  west 

Do . 

June  6,1916 

57 . 6 

of  Drake’s  Springs  in  meadow. 

May  16,1916 

26 

Do . 

July  14,1922 

62 

Do . 

June  6,1916 

26.8 

West  end  . 

. Do . 

43.5 

Do . 

July  14,1922 

29 

Middle . 

. Do . 

50.5 

The  Devil 

’s  Kitchen. 

[Elevation  about  5,800  feet.  Average  boiling-point  of  pure  water  for  this  elevation  about  94.0°  C.] 

Locality. 

Date. 

Temp. 

Locality. 

Date. 

Temp. 

°  c. 

°  C. 

No.  1 . 

July  5,1915 

94 

No.  12 . 

June  3,1916 

81 

Do . 

May  20,1916 

91 

Do.;  feeble  activity;  invaded  by 

Do . 

June  3,1916 

78 

stream . 

Aug.  17,1923 

72  2 

Do . 

June  20,1922 

47  and  56.5 

No.  13 . 

May  25  j  1916 

92 

Do.  two  different  points . 

Aug.  17,1923 

92.9,  93.8 

Do.;  white  mud,  3  inches  below 

Hot  rivulet  flowing  into  No.  1 . 

June  20, 1922 

83 

normal . 

June  20,1922 

91.5 

No.  2 . 

May  20,1916 

40 

Do . 

Aug.  17,1923 

91.8 

Do . 

Aug.  17,1923 

93.3 

No.  14  pool . 

June  8 , 1916 

79 

No.  3 . 

July  5,1915 

91 

Do . 

May  20,1916 

80 

Do . 

Mav  20,1916 

91 

Do . 

June  21 \ 1922 

43.5 

Do .  .  . 

June  3 , 1916 

92 

Do . 

Aug.  15,1923 

58  8 

Do . 

June  8 , 1916 

90 

Do.;  separate  pool . 

June  21 , 1922 

78 

Do . 

June  20  j 1922 

82 

Do.;  mud-pot  on  margin . 

Do. . 

91 

Do.  larger  and  more  violent  than 

Do. . ‘ . '. . 

. Do .  .  . 

92  2 

formerly . 

Aug.  17,1923 

91 

Do . 

Aug.  15,1923 

93  2 

No.  4.  Hot  stream  depositing  pyrite. .  .  . 

May  20,1916 

80.5 

No  15 . 

May  20,1916 

88 

Do . 

June  20, 1922 

83 

Do . 

June  3,1916 

92  6 

Do.  no  pyrite  visible.  .  . 

Aug.  17,1923 

88.2 

Do . 

June  8,1916 

93  1 

No.  5 . ' 

May  25,1916 

82 

Site  of  15;  steam  bole  . 

June  21 , 1922 

94 

Do . 

June  8, 1916 

82 

Do.;  insignificant . 

Aug.  15,1923 

Do . 

June  20,1922 

84 

No.  16 . 

June  3,1916 

92 

Do.  (1)  slightly  turbid;  boiling; 

Aug.  17,1923 

88.4 

Do . 

June  8,1916 

92 

(2)  sulphur-vellow  pool 

Do. 

92  .8 

Do.;  stream  just  above  terrace; 

Hot  turbid  spring  just  above  No.  5 . 

June  20,1922 

92.5 

source  under  rock . 

Aug.  15,1923 

75.1 

No.  6 . 

July  5,1915 

91 

No.  17 . 

Mav  20, 1916 

89  8 

Do.  (?) . 

June  20,1922 

71 

No.  18 . 

Do 

90 

No.  7 . 

July  5,1915 

85 

Do.  . . 

June  8 , 1916 

93 

Do . 

June  1,1916 

83 

No.  18;  new  spring  very  close  to  old  site.  . 

June  21 , 1922 

85 

Do.  west  border . 

June  20,1922 

65  5 

No.  19 . 

May  20,1916 

83 

Do.  slightly  turbid  (some  pyrite). 

Aug.  17,1923 

82.9 

Do . 

June  8,1916 

90 

Pool  5  feet  west  of  No.  7 . 

June  20,1922 

80 

Do.;  near  old  site . 

June  20,1922 

92  5 

No.  8 . 

June  1 , 1916 

62 

Do.;  very  active . 

Aug.  15,1923 

92 

Do  (?) . 

Tune  20,1922 

88.5 

No.  20 ......  . . 

May  20,1916 

92  3 

Do.;  gray  pool;  water  low . 

Aug.  17,1923 

79.1 

Do.;  near  old  site . 

June  21,1922 

94 

No.  9 . . 

June  20,1922 

85  and  88 

Do.;  activity  insignificant;  terraces 

Do.;  east  end . 

June  28, 1922 

86 

dry . 

Aug.  15,1923 

92.9 

Do.;  activity  about  normal . 

Aug.  17,1923 

87 

No.  21 . 

May  20,1916 

91 

No.  10.  Largest  mud  pot . 

July  5,1915 

94 

Do.;  near  old  site. . . 

June  21 , 1922 

84 

Do . ‘ . 

June  8,1916 

94 

Do.;  (nearly  dry).. 

Aug.  15,1923 

90  4 

Do . 

June  1 , 1916 

93 

No.  22 ... V . .  . .  ' 

June  21 , 1922 

93 

Do . 

June  20,1922 

93 

Do. ;  very  active . .  . 

Aug.  15,1923 

92  8 

Do.;  low . 

Aug.  17,1923 

92.6 

No.  23 . 

June  21  1922 

93 

No.  11.  Sulphur-yellow  pool . 

June  1,1916 

90 

Do.;  very  active.. . 

Aug.  15,1923 

93 

Do.  . ! . 

Aug.  17,1923 

83.8 

107 


Table  i.- — Continued. 


The  Devil’s  Kitchen — Continued. 


Locality. 

Date. 

Temp. 

Locality. 

Date. 

Temp. 

No.  24 . , . . 

[une  21,1922 

°  C. 

93 

No.  28 . 

June  28,1922 

°  C. 

82 

Do.;  very  active . 

Aug.  15,1923 

92.5 

Do.;  thick  black  scum;  little 

No.  25 .  . 

June  21,1922 

92 

bubbling . 

Aug.  17,1923 

56 

Do.;  very  active . 

Aug.  15,1923 

93 

No.  29.  Big  fumarole . 

June  20,1922 

94 

Steam  hole  near  No.  24  and  No.  25 . 

June  21 , 1922 

94 

Do.;  dry,  no  activity . 

Aug.  15  1923 

No.  26  .  . 

. Do . 

79,  92.5, 

No.  30.  Dry  steam  fumarole  (noisy).... 

. Do.  .  .  . 

94  1 

93.5 

No.  31.  Active . 

. Do . 

92  1 

Do . 

Aug.  15,1923 

94 

No.  32.  New  pool  (milky;  pyrite  scum; 

No.  27 . 

June  20,1922 

92.5 

no  outlet) . 

.  Do .  . 

77 

East  two  of  three  mud  pots . 

. Do . 

91.5,  92.5 

Bumpass  Hell. 

[Elevation  about  8,000  feet.  Average  boiling-point  of  pure  water  for  this  elevation  about  91.5°  C.] 

Locality. 

Date. 

Temp. 

Locality. 

Date. 

Temp. 

°  C. 

°  C. 

No.  1 . 

July  3,1922 

12 

No.  11  stream.  Continued. 

No.  2,  NW.  corner . 

. Do . 

55.5 

Do.;  east  of  No.  6,  4  feet  awav. . .  . 

Aug.  10,1923 

55  1 

No.  3,  east  end . 

. Do . 

59 

No.  12  spring  on  border  of  pool . 

July  3 i 1922 

50 

No.  4;  sulphur  pool;  opaque . 

June  5 , 1916 

85.5 

Do.  .  .7 . ' . 

. Do . 

87.5 

Do. . ' . ' .  . ' . 

July  3,1922 

84  to  85 

Do . 

Do . 

90 

Do.;  no  outflow;  18  inches  low.  .  .  . 

Aug.  IE  1923 

84.4 

Do.;  water  very  low . 

Aug.  10,1923 

89.3 

F umarole  15  feet  NW.  of  No.  4 . 

July  3,1922 

92 

No.  12.  New  fumarole;  inaccessible;  very 

No.  6 . 

Do.  ... 

34.6 

noisy . 

.  Do . 

Do.;  pool  low;  no  outflow . 

Aug.  11,1923 

55 

No.  13.  Large  fumarole . 

July  3,1922 

91 

Do.;  near  hot  south  bank . 

. Do . 

86.3 

Da.;  very  noisy;  little  water;  in- 

Black  mud-pot  NE.  of  6 . 

Do.  . 

89.8 

accessible . 

Aug.  10,1923 

No.  7,  at  outlet . 

July  3,1922 

42.5 

No.  14 . 

June  5,1916 

91 

Do.;  volume  small . 

Aug.  11,1923 

41.2 

Do.;  western  pool . 

July  3,1922 

91.5 

Do.;  eastern  branch . 

July  3,1922 

47.5 

Do.;  active  steam  and  water  spray. . 

Aug.  11,1923 

93 . 1 1 

Do.;  western  branch . 

Do.  . 

34.5 

Do.;  eastern  pool . 

July  3,1922 

90 

No.  8,  fumarole . 

June  5,1916 

1 17.5  max.1 

Do.  doubled  in  breadth  N-S 

Do . 

July  3,1922 

86 

since  1922  . 

Aug.  11,1923 

89  (S.  side) 

Do.;  (temp,  above  range  of  ther- 

Do.  eastern  pool  (continuous 

mometer) . 

Aug.  10,1923 

110. +1 

steam  and  water  spray  3  to  8 

No.  9 . 

July  3,1922 

88.5 

feet) . . . 

. Do . 

94. 11 

Do . 

Aug.  10,1923 

84.6 

No.  15 . 

J  une  5,1916 

85 

No.  10 . 

July  3 ’ 1922 

63 

Do . 

July  3 | 1922 

57 

{  89.4 

Do . 

Aug.  10,1923 

60 

Do.;  (more  active;  temp,  in  5 

89.8 

2  mud  pots  just  south  of  No.  15 . 

July  3,1922 

91.5 

places) . 

Aug.  10,1923 

92 

Do . 

. Do . 

92.51 

92. 51 

Mud  pots,  now  become  turbid  springs  (1) 

Aug.  10,1923 

90 

92.2 

Do.;  (2) . 

. Do . 

85.5 

No.  11,  stream . 

luly  3,1922 

19 

No.  16.  More  water  than  in  1922 . 

Aug.  11,1923 

91 

Do.;  east  of  No.  6 . 

Aug.  10  ’  1923 

88.5 

No.  17.  Black  muddy  pool . 

....  Do . 

89.8 

Mill  Creek  Springs. 

[  2  miles  south  of  Lassen  Peak  just  inside  the  oldest  crater  rim  east  of  Brokeoff  Mountain.  Elevation  7,950  feet. 

Average  boiling-point 

of  pure  water  for  this  elevation  about  91.5°  C.] 

Locality. 

Date. 

Temp. 

Locality. 

Date. 

Temp. 

°  C. 

°  c. 

2  boiling  springs;  sulphur  precipitate. .  .  . 

July  16,1915 

68 

Big  fumarole,  water  in  bottom :  Continued. 

Strongly  boiling  spring;  dark  precipitate 

. Do . 

90.2 

Do . 

Aug.  11,1923 

91,1 

Do.;  no  precipitation . 

Aug.  11,1923 

90.8 

Dry  fumarole;  sulphur  deposits  and 

Big  fumarole,  water  in  bottom: 

probably  ferric  salts . 

July  16,1915 

88.6 

In  steam . 

July  16,1915 

89.2 

In  water . 

July  16,1915 

90.8 

1  Note  that  these  temperatures 

are  above  t 

le  boiling  point  of  water  at  this  elevation. 

108 


Table  i. — Continued. 

Supan’s  Springs. 


Locality. 

Date. 

Temp. 

Locality. 

Date 

Temp 

0  C. 

0  C. 

Lower  Springs: 

Upper  Spring: 

No.  1.  Shallow  pool  bubbling  rapidly .  .  .  . 

Aug.  11,1923 

91  6 

Fountain  5  feet  high . 

Aug.  11,1923 

85.0 

No  ?  Small  turbid  sprintr . 

.  Do . 

87.4 

Pool  below  fountain . 

Do.  .  . 

83  5 

No  3  Do  ;  brown  sediment . 

. Do . 

86.2 

No.  4.  Large  mud  pot . 

. Do . 

63.8 

No.  5.  Mud  volcano  in  canyon;  bright 

blue,  terraced . 

. Do . 

91 .2 

Other  Field  Tests. 

Tests  with  lead-acetate  paper  showed  that  while  hydrogen  sulphide  was  widely 
distributed,  only  very  small  quantities  were  escaping  from  the  springs.  The  papers 
were  usually  browned  very  slowly.  These  tests  also  indicated  that  the  gases  do  not 
rise  uniformly  from  the  whole  spring  surface,  but  chiefly  if  not  entirely  from  certain 
points.  In  making  this  test,  by  the  way,  the  paper  should  not  be  dipped  into  the 
water,  but  held  just  above  it;  otherwise,  so  minute  is  the  amount  of  gas  actually 
dissolved  in  the  water  that  the  reagent  may  be  washed  away  before  any  effect  is 

Table  2. — Hot  Springs  of  Lassen  Peak  Region. 


[Unpublished  observations  by  J.  S.  D 1  Her,  1921.  Springs  may  be  identified  by  the  letters,  figs.  59  and  47.] 


No. 

Description. 

Date. 

Temp. 

1 

Western  belt: 

Morgans.  Biggest;  2  miles  north  of  stage  road.  Vigorously  boiling . 

1921 

June  19 

0  C. 
95.6 

2 

Do . 

June  22 

95.6 

3 

Morgans.  Biggest:  old  steam  bath  in  meadow  by  creek;  no  hot  water  seen . 

fune  19 

91.7 

4 

Morgans.  Big  Mill  C'reek,  50  vards  NW.  of  old  steam  bath . 

.  .  Do _ 

89  4 

5 

6 

Supan’s  Big  Boiler,  1  mile  NW.  of  Supan’s  cabin;  vigorously  boiling;  elevation 

7,675  feet,  not  accessible  at  that  time . . 

Supan’s  Big  Boiler,  as  No.  5,  but  water  low;  all  steam . 

June  21 
Aug.  14 

68.9 

7 

Bumpass  Hell,  west  side.  Steam  onlv;  hissing . 

Aug.  13 

88.9 

8 

Bumpass  Hell,  west  side.  Boiling  mud  pot  bv  No.  7 . 

. Do .  .  . 

88  3 

9 

Eastern  belt: 

Gevser,  boiling  vigorously . 

July  10 

93.9 

10 

Tartarus  Lake,  100  yards  west  of  inflow;  slow  boiling . 

June  9 

81.1 

11 

Tartarus  hake;  boiling  mud  pool  by  inlet  (forenoon) . 

June  10 

91.7 

12 

Tartarus  Lake;  boiling  mud  pool  bv  inlet  (afternoon) . 

fune  11 

90.6 

13 

Taratrus  Lake;  at  slide  40  vards  east  of  inlet;  hissing  steam . 

fune  13 

88.9 

14 

Tartarus  Lake;  west  side  near  mud  cone . 

fune  14 

47.8 

15 

Tartarus  Lake;  outlet . 

.  Do _ 

47  2 

16 

Do . 

June  28 
June  13 

50  6 

17 

Drake’s  Springs.  East  spring  of  line  south  of  creek . 

51.7 

18 

Do . 

fune  14 
July  10 
fune  14 

51  7 

19 

Do . 

58  9 

20 

Drake’s  Springs.  West  spring  of  line  south  of  creek .  . 

47.8 

21 

Do . 

Do.  . 

43  9 

22 

Do . 

July  10 
June  11 

44  4 

23 

Devil’s  Kitchen,  east  end;  sputtering  spring,  left  edge  of  creek . 

93.3 

24 

Devil’s  Kitchen,  east  end;  hissing  spring,  steam . 

...  Do . 

92.8 

25 

Devil’s  Kitchen;  east  end;  middle;  vigorously  boiling . 

.  Do _ 

93  3 

26 

Devil’s  Kitchen;  near  head,  150  yards  northeast  of  falls,  near-bv  mud  pot . 

...  Do . 

93  3 

27 

Devil’s  Kitchen;  near  head;  big  mud  pot . 

|une  12 

93.9 

28 

Devil’s  Kitchen;  near  head;  clear  pool  50  yards;  nearer  falls;  vigorously  boiling . 

June  28 

81.7 

109 


noticeable.  Certain  gases  issuing  from  fumaroles  and  ground  cracks  were  found  by 
the  same  test  to  contain  considerably  more  hydrogen  sulphide.  Tests  with  sensi¬ 
tive  litmus  paper  proved  that  most  of  the  waters  were  slightly  acid  or  neutral;  only 
a  very  few  were  slightly  alkaline. 

Tests  At  Camp. 

After  the  water  samples  had  cooled  in  the  collecting  bottles  they  were  filtered 
before  sealing1  for  shipment.  To  avoid  oxidation  the  filtering  was  done  as  rapidly 
as  possible  in  large  funnels  covered  wich  glass  plates,  or  if  the  samples  were  quite 
muddy  they  were  left  to  settle,  siphoned  off,  and  afterwards  filtered.  The  water 
from  mud  pots  (or  mud  volcanoes)  was  obtained  by  squeezing  the  mud  in  “muslin” 
bags,  in  which  most  of  the  sediment  was  retained  while  the  thinner  product  squeezed 
out  was  filtered  again  the  usual  way.  Half  a  dozen  bottles  of  mud  were  sometimes 
required  for  a  single  bottle  of  water.  For  the  washing  of  bottles  and  other  vessels  at 
camp  the  supply  of  water  was  fortunately  remarkably  pure. 

In  order  to  obtain  as  nearly  as  possible  the  composition  of  the  waters  as  they 
issued  from  the  ground,  ferrous  iron  and  free  acid  were  determined  at  the  camp. 

DETERMINAT ON  OF  FERROUS  IRON. 

For  the  ferrous-iron  determination  a  filtered  portion  of  water  was  acidified  with 
sulphuric  acid  and  titrated  with  standard  permanganate.  An  exact  determination 
would  of  course  have  demanded  a  removal  of  any  hydrogen  sulphide  before  the 
titration.  Fortunately  for  our  primitive  facilities,  the  amount  of  this  gas  retained 
in  the  spring  waters  was  rarely  enough  to  impart  to  them  the  slightest  odor,  and  a 
comparison  of  the  amount  of  ferrous  iron  with  the  total  iron  found  later  in  the 
laboratory  at  Washington,  proved  that  the  total  iron  was  nearly  always  equal  to  the 
ferrous  iron  or  in  slight  excess  over  it;  in  other  words,  that  the  iron  was  all,  or  nearly 
all,  ferrous — a  conclusion  in  excellent  accord  with  the  facts  of  field  observation. 
In  the  few  cases  where  the  ferrous  iron  found  was  slightly  greater  than  the  total 
iron  the  reason  is  evident,  and  it  is  justifiable  to  regard  the  iron  as  all  ferrous 
(see  page  1 13). 

DETERMINATION  OF  FREE  ACID. 

Another  change  in  composition  of  the  waters,  which  might  naturally  occur 
after  collection  and  before  they  came  to  be  analyzed,  was  an  increase  in  free  acid  due 
to  hydrolysis  of  ferric  salts  which  might  result  from  oxidation.  The  free  acid  was 
therefore  determined  at  camp.  For  this  purpose  the  waters  were  titrated  with 
dilute  sodium  carbonate  with  the  use  of  methyl  orange  as  indicator.  The  method 
would  have  been  satisfactory  had  not  the  standard  alkali  taken  been  unsuitably 
dilute.  On  this  account  the  errors  are  greater  than  they  would  have  been  with 
sufficient  laboratory  facilities  at  hand. 

1  An  excellent  method  of  sealing  samples  of  this  character  is  to  melt  Khotinsky  cement  around  the  carefully  dried  stopper 
of  the  bottle.  An  alcohol  blow-torch  is  best  adapted  to  field  work. 


110 


WORK  IN  THE  LABORATORY. 

The  Waters. 

A  few  remarks  will  be  necessary  in  regard  to  water  analyses.  In  some  cases 
when  the  bottle  was  opened  a  precipitate  of  ferric  oxide  was  found  clinging  to  the 
walls.  In  this  event  the  total  volume  of  the  water  was  measured  and  the  iron  as 
well  as  S04  in  the  precipitate  was  determined,  so  that  corrections  might  sub¬ 
sequently  be  applied.  Since  boric  acid  has  been  regarded  by  geologists  in  the  past 
as  of  some  critical  importance  in  judging  of  the  origin  of  spring  waters,  the  determi¬ 
nations  of  this  constituent  were  made  with  unusual  care.  Chapin’s  method  1  was 
used.  A  measured  volume  of  water  was  first  evaporated  to  dryness  on  the  steam 
bath  with  a  slight  excess  of  sodium  hydroxide.  The  residue  was  transferred  with 
15  c.  c.  water  in  successive  portions  to  the  distilling  flask  and  acidified  with  hydro¬ 
chloric  acid.  After  a  small  excess  of  acid  had  been  added,  15  grams  of  anhydrous 
calcium  chloride  were  put  in  and  the  boric  acid  was  distilled  and  titrated  as  Chapin 
recommends.  A  blank  was  then  carefully  made  in  a  similar  manner.  It  amounts 
under  such  conditions  2  to  about  0.7  mg.  B2  03.  A  very  little  boric  acid  appeared 
to  be  present  in  practically  all  the  waters,  though  the  quantities  found  in  many 
cases  were  so  small  as  to  make  this  uncertain.  A  sample  of  lava  from  the  region 
also  gave  0.03  per  cent  B2  03  by  the  same  analytical  method. 

Lithium  was  tested  for  in  one  sample  from  each  of  the  three  principal  hot- 
spring  groups.  Only  100  c.  c.  water  was  taken.  The  mixed  alkali  chlorides, 
separated  in  the  usual  way,  were  tested  spectroscopically.  No  lithium  was  observed. 

The  same  waters  all  showed  traces  of  manganese  when  tested  colorimetrically 
with  ammonium  persulphate  and  silver  nitrate. 

The  percentages  of  carbon  dioxide  given  in  the  tables  represent  total  carbon 
dioxide  both  free  and  combined.  The  amount  of  th t  Jree  gas,  however,  was  doubt¬ 
less  negligible  in  waters  of  this  temperature  range.3 

Small  quantities  of  the  water  samples,  generally  100  c.  c.,  sometimes  200  c.  c., 
were  taken  for  the  analytical  determinations.  The  inconvenience  of  transporting 
large  samples  practically  precluded  the  use  of  larger  portions.  Errors  were  thus 
multiplied  by  5  or  generally  by  10.  So  far  as  we  can  see,  however,  the  results  are 
accurate  enough  for  all  uses  to  which  they  are  likely  to  be  put.  The  results  are 
stated  in  milligrams  per  liter,  not  reduced  to  parts  per  million. 

PECULIARITIES  IN  THE  COMPOSITION  OF  THE  WATERS. 

In  composition  all  the  hot-spring  waters  from  the  Lassen  region  (see  table  3) 
which  we  have  examined,  though  they  vary  considerably  in  concentration,  namely, 
from  o.n  gram  to  1.59  grams  per  liter,  show  striking  similarities.  They  are  with¬ 
out  exception  sulphate  waters  almost  entirely  free  from  chlorides.  The  sulphates  are 
those  of  the  common  rock  bases ,  with  the  exception  of  alumina ,  which,  in  four-fifths  of 
the  samples,  varies  from  o  to  0.2  mg.  per  100  c.  c.,  the  amount  used  in  analysis. 

1  Journ.  Amer.  Chem.  Soc.,  30,  1687,  1908. 

2  E.  T.  Allen  and  E.  G.  Zies,  Journ.  Amer.  Ceram.  Soc.,  1,  763,  1918. 

3  At  the  time  the  analyses  were  made  it  was  believed  that  practically  all  the  carbon  dioxide  was  in  the  form  of 
bicarbonate.  It  is  now  known  that  carbonate  is  present  in  at  least  some  of  the  alkaline  waters. 


Ill 


Iii  other  words,  four-fifths  of  the  waters  examined  are  virtually  free  from  alumina. 
The  more  acid  waters  contain  more  alumina. 

In  considering  the  condition  of  the  iron  in  the  waters  it  will  be  noticed  that  the 
water  from  the  Boiling  Lake  contains  only  ferric  iron,  while,  with  a  single  exception, 
(No.  23,  table  3),  the  springs  and  similar  pools  contain  almost  no  ferric  iron.  The 
volume  of  gases  escaping  from  the  lake  appears  to  be  relatively  small,  and  their 


Table  3. — Composition  of  hot-spring  waters  in  milligrams  per  liter. 

Boiling  Lake. 


Sam¬ 

ple 

No. 

Map 

No. 

H 

nh4 

K 

Na 

Ca 

Mg 

Fe" 

Fe,,, 

Al 

so4 

|  Cl 

Si02 

co2 

BA 

Water  of  the  lake 

from  near  the 
foot 1 . 

1 

7.5 

none 

(2) 

10 

7 

4.8 

none 

26 

8 

514 

trace 

84 

0.7 

Water  of  the  lake 

from  the  west 
side  1 . 

3 

6.7 

(2) 

20 

12 

4.4 

none 

27 

9  6 

516 

106 

Water  of  the  lake 

from  near  the 
head  1 . 

2 

7.1 

(2) 

10 

9.3 

4.5 

none 

27 

14.0 

516 

72 

Vigorously  boiling 

spring  near  head 
of  lake.  Waters 
collected  May  19, 
1916 . . 

13 

4 

2 

9.7 

6 

22 

44 

18 

18 

none 

1 

258 

trace 

111 

The  same  spring. 

Watei  collected, 

J une  8 . 

131 

4 

6 

20 

30 

8 

29 

none 

none 

291 

trace 

123 

none 

Black  mud  spring 

boiling  vigorously. 
Black  mud  spring. .  . 
Mud  volcano . 

128 

1 

none 

19  3 

7 

31 

54 

33 

197 

none 

2 

775 

trace 

265 

0  7 

15 

5 

none 

19  3 

6 

26 

23 

none 

26 

9 

2 

269 

trace 

202 

0  6 

125 

7 

0.57 

none 

1  8 

5.5 

14 

8 

104 

4 

2 

322 

1 

68 

0.7 

Devil’s 

Kitchen. 

Mud  volcano,  larg- 

est  in  the  basin  . 

362 

10 

none 

2.8 

14 

38 

29 

none 

45 

6 

1.9 

248 

6 

222 

1 

Mud  volcano,  ex- 

tremely  active. .  .  . 
Black  mud  spring. .  . 
Vigorously  boiling 

331 

13 

trace 

3  8 

12 

58 

10 

5 

153 

none 

1.5 

4?? 

4.0 

213 

none 

23 

18 

none 

50.6 

10 

37 

61 

17 

6 

75 3 

none 

527 

trace 

212 

soring . 

21 

21 

acid3 

8.8 

9 

22 

16 

5 

36 

none 

2.5 

244 

trace 

89 

1 

Small  spring,  high 

level . 

37 

15 

.38 

2.8 

4 

12 

9 

2 

4 

3 

2 

95 

1.7 

74 

1 

Violently  boiling 

spring,  faintly 
alkaline . 

31 

1 

none 

none 

4 

16 

9 

3 

none 

none 

none 

36 

trace 

45 

1 

Violently  boiling 

alkaline  spring.  .  . 
Small  quiet  spring, 

29 

3 

none 

5 

23 

21 

9 

none 

none 

none 

58 

1.0 

63 

72 

0.6 

3 

97 

May  20,  alkaline. 
Same  as  22,  collect- 

22 

19 

none 

11 

55 

24 

none 

none 

none 

95 

none 

217 

2.0 

ed  June  8. . . . 

221 

19 

none 

8 

33 

14 

1 

none 

none 

none 

78 

none 

218 

55 

Large  pool  fed  by 

springs . 

30 

5 

7 

2.6 

9 

43 

38 

14 

30 

none 

10 

617 

trace 

167 

1 

1  These  samples  of  lake  water  were  collected  by  Mr.  Sifford  in  the  autumn  of  1915. 

2  Sodium  and  potassium  not  separated;  all  alkali  chloride  calculated  as  NaCl. 

3  This  is  probably  an  error  (see  p.  113). 


112 


Table  3. — Continued. 
Bumpass  Hell. 


Sam- 

Map 

No. 

pie 

No. 

H 

nh4 

K 

Na 

Ca 

Mg 

Fe" 

Fe'" 

A1 

so4 

Cl 

Si02 

C02 

b2o3 

Very  large,  violently 
boiling  spring .... 
Hot  pool  filled  with 

60 

14 

7 

15 

13 

29 

7 

4.5 

17.5 

5 

28 

681 

2 

236 

4 

precipitated  sul¬ 
phur  . 

62 

15 

none 

128 

4 

33 

7 

2 

4 

'  4 

none 

419 

trace 

138 

84 

Largest  hot  pool, 

filled  with  precipi¬ 
tated  sulphur .... 

64 

4 

4 

39.6 

2 

21 

5 

trace 

29 

9 

32 

613 

trace 

224 

21 

Large  pool  covered 

with  a  scum  of 

nvrite . 

63 

6 

8.9 

11.4 

13 

42 

37 

25 

51 

23 

1010 

trace 

358 

Drake 

s  Springs.1 

Easternmost  spring 
south  side  of 
Warner  Creek. . .  . 

400 

none 

10.5 

34.6 

53 

13 

none 

none 

none 

152 

136 

20 

1  The  analysis  of  this  slightly  alkaline  water  is  not  complete;  the  acid  radicals  are  insufficient  to  balance  the  basic  ele¬ 
ments.  The  determinations  were  repeated  and  found  essentially  correct.  Also,  the  alkalinity  of  the  water  was  determined 
by  a  very  weak  hydrochloric-acid  solution  and  found  to  be  equivalent  to  the  carbon  dioxide  found  when  reckoned  as  all  in 
the  form  of  bicarbonate.  Unfortunately  the  water  sample  was  insufficient  for  further  investigation. 

reducing  or  protecting  influence  is  probably  insufficient  to  prevent  atmospheric 
oxidation. 

The  maximum  amount  of  ferric  iron  found  in  any  of  the  other  samples,  with  the 
exception  just  noted,  is  9  mg.  per  liter,  or  0.9  mg.  in  the  volume  usually  taken  for 
analysis.  A  careful  scrutiny  of  the  results  indicates  that  these  values  for  ferric 
iron,  which  of  course  represent  the  difference  between  the  values  for  the  total  iron 
and  the  ferrous  iron,  are  within  the  limits  of  error.  In  the  collection  of  the  samples 
the  bottles  were  filled  with  water,  stoppered  as  tightly  as  possible,  and  the  stopper 
tied  down  with  a  cloth  hood.  The  samples  were  not  opened  until  cold.  No  appre¬ 
ciable  oxidation  could  have  taken  place  in  this  time.  In  the  subsequent  filtration 
the  waters  from  the  mud  volcanoes  were  exposed  for  a  longer  time  to  the  air  and 
under  conditions  more  favorable  for  oxidation  than  the  other  samples,  yet  no  more 
ferric  iron  was  found  in  them.  Thus  in  No.  125,  which  was  taken  from  mud  volcano 
No.  7,  Boiling  Lake,  only  4  mg.  of  ferric  iron  per  liter  was  found,  and  in  No.  362  and 
No.  331,  waters  from  mud  volcanoes  No.  10  and  No.  13,  Devil’s  Kitchen,  6  mg.  and 
o  mg.  respectively  were  found.  Still  more  significant  is  the  analysis  of  No.  64  of 
the  water  from  spring  No.  4,  Bumpass  Hell.  This  water  contained  enough  hydro¬ 
gen  sulphide  to  impart  to  it  a  distinct  odor  when  cold,  and  when  the  ferrous  iron 
was  determined  at  the  camp  the  iron  was  doubtless  all  in  the  ferrous  condition,  yet 
the  maximum  amount  of  ferric  iron,  9  mg.  per  liter,  was  found.  Thus,  while  labor¬ 
atory  methods  now  in  vogue  are  quite  competent  to  decide  a  question  of  this  sort, 
the  primitive  camp  facilities  under  which  some  of  the  work  had  to  be  done  leave  us 
in  doubt  whether  the  spring  waters  generally  contain  no  ferric  iron  at  all  or  only  a 


113 


very  little.  The  latter  view  is  in  better  accord  with  field  evidence,  for,  as  pre¬ 
viously  stated,  the  volcanic  gases  contain  only  a  small  amount  of  hydrogen  sul¬ 
phide  and  they  rise  here  and  there  from  occasional  points  of  the  surface,  not  uni¬ 
formly  over  the  whole  pool,  and  furthermore  the  waters  are  hot,  only  slightly  acid  at 
the  best,  and  often  more  effectively  exposed  to  the  air  by  spouting.  All  these  con¬ 
ditions  favor  oxidation.  Indeed,  if  there  is  no  oxidation  at  all  it  is  not  easy  to  ex¬ 
plain  the  formation  of  pyrite  which  other  facts  support.  Oxidation  and  reduction 
involving  small  amounts  of  iron  are  probably  following  each  other  continually  at 
the  surface  of  the  spring  pools. 

The  analysis  of  sample  No.  23  from  spring  No.  18,  Devil’s  Kitchen,  presents  a 
different  case  from  the  rest;  75  mg.  of  ferric  iron  were  found  in  this  water  and  only  6 
mg.  of  ferrous  iron.  The  spring  from  which  it  was  taken  was  a  black  mud  spring 
which  was  shown  by  microscopic  examination  to  contain  a  quantity  of  minute 
pyrite  crystals,  some  as  small  as  0.01  mm.  diameter,  and  while  these  might  slowly 
oxidize  in  the  spring  or  during  filtration,  all  previous  experience  indicates  that 
ferrous  salt,  not  ferric,  would  be  the  principal  product.  This  conclusion  is  supported 
by  the  analysis  of  samples  Nos.  15  and  128.  Both  these  waters  were  from  black 
mud  springs  and  the  ferric  iron  found  in  them  was  9  mg.  and  o  mg.  respectively. 
The  result  in  question  is  therefore  doubtless  incorrect  and  is  probably  affected 
by  some  crude  error  in  the  determination  of  ferious  iron  at  the  camp. 

We  conclude,  then,  that  the  iron,  one  of  the  principal  constituents  of  the 
waters,  is  nearly  all  in  the  ferrous  state. 

REACTION  OF  THE  WATERS. 

None  of  the  waters  of  these  hot  springs  is  very  far  from  neutrality.  Of  those 
analyzed  6  were  practically  neutral,  4  were  alkaline,1  and  8  were  acid.  The  acidity 
ranged  from  19  mg.  to  436  mg.  H2S04  per  liter,  that  is,  from  0.002  to  a  trifle  over 
0.04  weight  per  cent.  As  S04  is  practically  the  only  acid  radical  present  it  is  per¬ 
missible  to  state  the  results  in  this  simple  form.  Qualitative  tests  in  the  field  indi¬ 
cated  that  most  of  the  waters  were  slightly  acid. 

Salt  Incrustations.2 

Among  the  solid  products  collected  about  the  hot  springs  were  soluble  salts, 
patches  of  which  appeared  at  times  here  and  there  on  the  dry  ground  in  all  the  hot- 
spring  areas.  The  patches  were  never  very  large;  generally  not  more  than  a  few 
square  yards  in  extent  and  perhaps  0.5  inch  in  thickness.  In  1916  some  patches 
were  found  in  all  the  areas3  visited  and  the  amounts  increased  as  the  season  ad¬ 
vanced,  but  in  June  and  July  1922,  when  the  snow  lingered  late  and  the  ground  in 
consequence  was  wetter  at  the  same  period,  scarcely  any  were  to  be  seen.  As  a 

1  Waring  (Springs  of  California,  p.  142)  cites  a  single  analysis  of  one  of  the  springs  of  the  Morgan  group  which  was  made 
by  F.  M.  Eaton  (1909-1910).  He  designates  the  pool  from  which  the  water  was  taken  as  “about  3  feet  in  diameter  in  an 
area  of  hard  siliceous  deposit  45  yards  west  of  the  creek  edge  and  50  yards  north  of  the  eastern  log  bath  house.”  1  he  analysis 
in  parts  per  million  follows:  Na  1416,  K  122,  Ca  90,  Mg  trace,  A1  +  Fe  2.2,  SO  4  102,  Cl  2342,  CO  3  25,  BO  2  present, 
SiO  2  200.  It  may  be  pointed  out  that  this  water  is  very  similar  to  one  of  the  slightly  alkaline  waters  found  in  the  Devil’s 
Kitchen  and  to  the  sample  from  Drake’s  Springs  with  the  addition  of  an  excess  of  sodium  chloride. 

2  The  microscopic  examination  was  made  by  H.  E.  Merwin. 

3  Except  Drake’s  Springs,  where  the  ground  is  covered  with  vegetation. 


114 


result  of  these  observations  the  salt  patches  were  at  first  supposed  to  bear  a  very 
simple  relation  to  the  dryness  of  the  ground,  but  later  observations  (August  1923) 
showed  that  even  in  very  dry  times  the  salts  may  not  occur  at  all  (seep.  157).  Usu¬ 
ally  these  salts  formed  fibrous  aggregates,  varying  in  color  from  white  to  yellow, 
according  to  the  percentage  of  ferric  iron  they  contained.  All  the  samples  were 
collected  in  May  and  June  1916. 

No.  43  was  found  under  a  small  rock  in  the  Geyser  ravine,  on  the  west  side  of 
the  little  stream  and  a  few  steps  below  the  lowest  pool.  A  small  fumarole  issued 
here.  The  product  was  white  and  mixed  with  siliceous  residue. 


Fig.  59. — Sketch  Map  of  the  Boiling  Lake  (Tartarus)  showing  location  of  the 

springs  in  June,  1916. 


No.  150  was  from  the  delta  at  the  south  end  of  the  Boiling  Lake  on  the  bank  of 
the  stream  which  forms  the  inlet  (fig.  59).  This  bank  was  riddled  by  fumarolic 
action.  When  kicked  to  pieces  by  the  foot  it  revealed  pockets  of  fluffy,  fibrous  salt 
at  various  depths.  The  sample  analyzed  was  scraped  from  the  surface.  Another 
sample  collected  in  1915  from  the  bank  at  the  southeastern  corner  of  the  lake 
showed  a  similar  composition,  but  was  yellower  and  contained  more  ferric  iron. 

No.  26  was  collected  in  the  lower  end  of  the  Devil’s  Kitchen  a  few  steps  north 
of  No.  17  (fig.  47).  This  salt  patch  was  much  thicker  at  some  times  than  at  others, 
a  variation  doubtless  depending  on  the  weather. 

No.  61  was  found  at  Bumpass  Hell,  some  yards  up  on  the  southern  edge  of  the 
basin,  east  of  No.  9  (fig.  50).  Phis  patch  was  comparatively  thick  and  extensive, 
and  had  a  curious,  disagreeable,  persistent  odor  resembling  fertilizer.  Sample  No. 
26  had  a  similar  odor. 


115 


Besides  the  above  samples  we  collected  several  from  the  summit  of  Lassen 
Peak  which  are  products  ot  fumarolic  action  and  which  are  interesting  to  compare 
with  those  from  the  hot-spring  areas. 

No.  53  was  scraped  from  the  rocks  in  the  middle  of  the  crater,  where  it  formed 
a  thin,  closely  coherent  coating.  A  small  amount  was  obtained  from  three  different 
spots,  all  of  which  appeared  to  be  similar.  The  salts  were  all  of  deep-orange  color 
(due  to  ferric  chloride)  and  hydrochloric  acid  in  process  of  volatilization  was 
detected  along  adjacent  cracks. 

No.  51  and  No.  52  were  collected  on  different  dates  from  the  eastern  rim  of 
Lassen  Peak,  175  feet  below  the  highest  point  of  the  summit  and  some  distance  to 
the  north  of  it.  The  spot  where  sample  No.  52  was  collected  was  near  a  fumarole 
which  was  then  (1916)  very  active,  issuing  from  a  fissure  under  a  rock  about  50  feet 
east  of  the  crater’s  edge.  No.  51  was  found  in  the  same  general  vicinity.  By  1922 
this  fumarole  had  entirely  disappeaied,  but  tenuous  wisps  of  steam,  which  were  all 
but  invisible,  still  escaped  from  various  parts  of  the  crater  and  a  slight  odor  of 
hydrochloric  acid  was  still  detectable  in  some  places. 

ANALYSIS  OF  THE  SALTS. 

As  the  salts  could  not  be  obtained  free  from  insoluble  matter  they  had  first 
to  be  dissolved  and  filtered.  In  the  earlier  portion  of  the  work  the  solutions  were 
evaporated  to  “dryness”  on  the  steam-bath  and  the  residue  was  ground  in  a 
mortar,  but  the  material  so  prepared  was  probably  not  always  homogeneous,  for 
the  analyses  of  several  samples  proved  unsatisfactory.  In  such  cases  the  work  was 
repeated  in  a  manner  better  suited  to  the  nature  of  the  material.  A  solution  was 
first  prepared  from  a  suitable  sample  and  measured  portions  were  taken  for  the 
various  determinations.  Homogeneity  was  thus  assured,  gain  or  loss  of  water  by  the 
salt  during  weighing  was  avoided,  and  since  the  composition  of  the  soluble  portion 
only  was  required,  the  percentage  of  each  constituent  was  calculated  on  the  basis  of 
the  total  thus  found.  The  equivalence  of  acids  and  bases  furnished  sufficient  proof 
of  satisfactory  analytical  work.  The  details  of  analysis  require  no  description 
except  in  the  case  of  Nos.  51  and  52  from  Lassen  Peak,  which  are  of  a  character  so 
unusual  that  a  laborious  examination  was  necessary.  As  salts  of  similar  nature 
probably  occur  elsewhere  in  volcanic  regions,  the  analytical  procedure,  which  is  not 
to  be  found  in  the  textbooks,  is  recorded  here. 

DETERMINATION  OF  PENTATHIONATE. 

The  singular  behavior  of  some  of  the  salts  was  first  revealed  in  the  attempt  to 
separate  the  insoluble  matter  from  one  of  the  samples;  the  filtered  solution  when 
evaporated  on  the  water-bath  gave  off  sulphur  dioxide.  It  should  be  stated  in  this 
connection  that  the  salts  originally  showed  a  decidedly  acid  reaction.  Still  more 
curious  was  the  formation  of  a  yellow  precipitate  with  silver  nitrate  and  the  precipi¬ 
tation  of  “manganese  dioxide”  when  the  acidified  solution  of  the  salt  was  treated 
cold  with  permanganate.  These  reactions  indicate  thionates,  but  do  not  decide 
whether  one  or  all  four  thionates  are  present,  nor  do  they  exclude  sulphite,  thio¬ 
sulphate,  or  sulphate.  As  the  thionates  are  not  generally  known,  and  as  our  in¬ 
formation  concerning  them  is  thus  more  liable  to  be  in  error,  preparations  of  all  of 


116 


them  were  made  for  the  purpose  of  studying  their  reactions  qualitatively  and 
quantitatively.  About  half  a  dozen  tests  (already  known)  were  found  useful  in 
the  investigation. 

(1)  The  unknown  when  evaporated  to  dryness  gave  free  sulphur  and  sulphur  dioxide. 
All  the  thionates  except  dithionates  respond  to  this  test  as  do  also  the  thiosulphates. 

(2)  With  permanganate  in  the  cold  the  acidified  solution  of  the  unknown  gave  a 
brown  precipitate.  This  reaction  is  given  by  the  same  compounds  as  reaction  1. 

(3)  When  the  unknown  was  boiled  with  a  solution  of  mercuric  cyanide  a  black  preci¬ 
pitate  was  obtained.  This  reaction  is  characteristic  of  all  the  thionates  except  dithionates. 
It  is  characteristic  also  of  the  thiosulphates. 

(4)  With  mercurous  nitrate  the  unknown  gave  at  first  a  yellow  precipitate,  which  gradu¬ 
ally  turned  black.  Pentathionates  and  tetrathionates  behave  similarly,  while  trithionates 
and  thiosulphates  give  black  precipitates.  This  test  therefore  indicates  pentathionates, 
tetrathionates,  or  both,  but  does  not  exclude  dithionates  and  perhaps  not  trithionates,  at 
least  in  small  amounts. 

(5)  With  iodine  solution  and  excess  of  soluble  bicarbonate,  one  sample  of  the  unknown 
absorbed  no  iodine,  another  sample  only  a  trace.  This  test  excludes  sulphites  and  thio¬ 
sulphates  with  certainty. 

(6)  With  ammoniacal  silver  nitrate  solution  the  unknown  gave  a  black  precipitate.  This 
proves  the  presence  of  pentathionate  with  the  possible  presence  of  dithionate,  tetrathionate, 
and  trithionate,  which  do  not  react  with  the  reagent.  Small  amounts  of  pentathionate 
may  be  detected  in  this  way  in  the  presence  of  large  quantities  of  tetrathionate,  though  the 
solution  must  be  cold.  Thus  1  mg.  of  the  pentathionate  radical  S5  06  may  be  detected 
in  about  140  c.  c.  of  solution.  Tetrathionate  does  not  respond  to  the  reagent  in  a  con¬ 
centration  of  1  gram  of  the  radical  S4  06  in  1.3  c.  c.  water,  even  after  one  hour. 

(7)  When  the  unknown  was  boiled  for  some  minutes  with  a  few  drops  of  cupric 
sulphate  solution  no  precipitate  was  obtained.  Under  these  conditions  a  soluble  trithionate 
gives  a  black  or  dark-brown  precipitate,  said  to  be  cuprous  sulphide.  The  test  is  moderate¬ 
ly  delicate.  Thus  5  c.  c.  of  a  solution  of  potassium  trithionate  containing  0.1  mg.  of  the 
salt  per  cubic  centimeter  gave  a  plain  test  after  boiling  for  a  few  minutes.  The  test  was 
also  obtained  by  boiling  down  to  half  its  volume  5  c.  c.  of  the  above  solution,  to  which 
had  been  added  1  gram  of  alum  to  make  it  comparable  in  composition  to  the  unknown. 
But  50  c.  c.  of  a  trithionate  solution  containing  the  same  amount  of  salt,  0.5  mg.,  did  not 
respond  to  the  test  with  copper  sulphate,  even  when  boiled  down  to  a  very  small  volume. 
From  this  we  may  conclude  that  the  unknown  contains  only  a  very  small  amount  of  tri¬ 
thionate,  if  any. 

As  a  result  of  all  the  tests  we  find  that  pentathionate  is  certainly  present,  tetra¬ 
thionate  and  dithionate  may  possibly  be  present,  as  well  as  a  very  small  amount  of 
trithionate.  It  should  also  be  remembered  that  none  of  the  tests  exclude  sulphate. 
To  determine  whether  the  doubtful  radicals  were  present  or  absent  quantitative 
experiments  were  necessary.  Dithionates  were  excluded  in  two  ways.  First  the 
dilute  solution  of  the  unknown  was  boiled  with  bromine.  This  oxidizes  all  soluble 
thionates  except  dithionates  to  sulphate.  In  the  resulting  solution  all  the  sulphate, 
including  of  course  any  which  was  originally  present,  was  precipitated  as  barium 
sulphate  and  eventually  filtered  off.  The  filtrate  containing  excess  of  barium 
chloride  was  then  evaporated  to  dryness  with  concentrated  nitric  acid.  In  this 
way  all  dithionate  is  transformed  into  barium  sulphate;  1.6  mg.  of  BaS04  was 
found.  Again  another  portion  of  the  unknown  was  precipitated  with  mercuric 


117 


cyanide.  The  precipitate  thus  formed  from  either  tetrathionate  or  pentathionate 
consists  of  mercuric  sulphide  and  tree  sulphur.  The  reactions  are  represented  by 
the  following  equations: 

(1)  K2S506  +  Hg(CN2)  +  2H20  =  2KCN  +  HgS  +  2S  +  2H2S04 

(2)  K2S406  +  Hg(CN2)  +  2H20  =  2KCN  +  HgS  +  S  +  2H2S04 

After  filtering  oft  the  precipitate  all  the  sulphur  in  solution  will  be  in  the  form 
of  sulphate  unless  dithionate  is  present.  The  sulphate  was  precipitated  as  before, 
and  in  the  filtrate  from  it  dithionate  was  sought  in  the  same  way;  1.3  mg.  BaS04 
was  found.  These  two  quantities,  1.6  mg.  and  1.3  mg.  BaS04  represent,  approxi¬ 
mately  at  any  rate,  the  solubility  of  barium  sulphate  under  the  present  conditions, 
and  it  is  safe  to  conclude  that  no  dithionate  is  present.  The  results  therefore  nar¬ 
row  down  the  possible  sulphur  compounds  in  the  salts  from  Lassen  Peak  to  tetra- 
thionates,  pentathionates,  and  sulphates.  The  two  thionates,  though  relatively 
stable  under  the  field  conditions  prevailing  where  the  salts  occurred,  are  very 
unstable  in  solutions  of  oxidizing  agents  and  alkaline  reagents,  especially  when  hot, 
and  these  facts  caused  a  great  deal  of  trouble  in  their  determination.  In  the  inter¬ 
est  of  accuracy  many  attempts  were  made  to  remove  the  sulphates  as  well  as  the 
iron  and  alumina  before  the  thionate  was  determined,  but  the  instability  of  the 
latter  proved  an  insurmountable  obstacle.  The  best  method  of  procedure  found 
was  to  separate  first  the  soluble  salts  from  rock  residue  and  free  sulphur  by  means 


Table  4. — Analyses  of  Soluble  Salts,  Products  of  Fumarolic  Action  in  the  Lassen 

National  Park. 


No . 

Locality. . . 

43. 

Geyser. 

150. 

Boiling 

Lake. 

26. 

Devil’s 

Kitchen. 

61. 

Bumpass 

Hell. 

51. 

Lassen  Peak, 
NE.  summit. 

52.1 

Lassen  Peak, 
NE.  summit. 

52.2 

Lassen  Peak, 
NE.  summit. 

53. 3 

Lassen  Peak, 
middle  of 

crater. 

A! . 

12.40 

10.70 

10.93 

8.93 

8.76 

8.10 

10.42 

13.28 

Fe"' . 

.63 

1  28 

trace 

1  01 

1 .38 

Fe" . 

trace 

.11 

8.93 

7.23 

5.60 

4.04 

3.11 

.27 

Ti . 

02 

09 

11 

04 

19 

11 

Mn . 

.06 

.07 

01 

03 

.04 

Mg . 

1.78 

3.10 

.06 

.91 

1.77 

1.72 

1.94 

2.53 

Ca . 

1.12 

.44 

none 

.10 

2.26 

1.51 

none 

1.00 

Li . 

present 

trace 

trace 

Na . 

1.51 

‘2.68 

.28 

.41 

1.83 

1.77 

2.13 

3.02 

K . 

.49 

.42 

.25 

.37 

.57 

.61 

.55 

.07 

(NH4) . 

.57 

.04 

07 

06 

H . 

19 

cal  26 

04 

cal.  .21 

25 

Cl . 

none 

none 

none 

none 

none 

none 

none 

20.74 

SO; . 

81.51 

81.14 

79.19 

80.58 

77.32 

72.09 

78.93 

57.63 

S5O6 . 

none 

none 

none 

none 

1.80 

9.77 

2.94 

none 

S4O6 . 

none 

none 

none 

none 

probably  none 

probably  none 

probably  none 

none 

S306 . 

none 

none 

none 

none 

none 

none 

none 

none 

STL . 

none 

none 

none 

none 

none 

none 

none 

none 

SO;, . 

none 

none 

none 

none 

none 

none 

none 

none 

BAi . 

none 

none 

none 

none 

none 

none 

none 

none 

1  Analysis  of  the  original  salt.  It  was  intermixed  with  about  2  per  cent  of  free  sulphur. 

2  Analysis  of  the  salt  obtained  by  extracting  original  with  water  and  evaporating  on  the  steam  bath. 

3  This  analysis  is  defective  but  is  included  to  show  the  general  character  of  the  mixture. 


118 


of  cold  water,  and  then  to  analyze  the  solution.  Probably  the  best  method  we 
have  of  determining  the  two  thionates,  either  alone  or  together,  is  by  weighing  the 
precipitate  from  a  given  quantity  of  salt  thrown  down  by  mercuric  cyanide  and 
then  to  ascertain  the  ratio  of  mercuric  sulphide  to  free  sulphur  in  the  precipitate. 
Reference  to  the  above  equations  shows  that  the  precipitate  from  tetrathionate 
contains  i  mol  free  sulphur:  i  mol  mercuric  sulphide,  while  that  from  pentathionate 
contains  2  mols  sulphur:  1  mol  sulphide. 

In  practice  the  ratio  was  determined  by  transforming  all  the  sulphur  in  the 
precipitate  to  barium  sulphate  and  finding  its  weight.  The  following  is  the  most 
satisfactory  of  the  results: 

Weight  of  HgS  +  xS  from  a  given  amount  of  solution  =  0.0474  gram. 

Weight  of  BaS04  from  the  sulphur  of  the  precipitate=o.  1 129  gram. 

0^74  _  HgS  +  xS  _  x  = 

0.1129  (1  +  x)BaS04 

From  this  and  other  determinations  it  was  concluded  that  no  more  than  a  few  tenths 
of  1  per  cent  of  tetrathionate  could  be  present  and  probably  none  at  all. 

After  the  pentathionate  had  been  thus  determined,  the  total  sulphur  was 
obtained  by  the  oxidation  of  the  pentathionate  to  sulphate  by  bromine  and  the 
subsequent  precipitation  of  all  sulphate  as  barium  sulphate.  The  sulphate  origi¬ 
nally  present  was  then  determined  by  difference. 

The  analyses  of  all  the  salts,  both  from  Lassen  Peak  and  from  the  hot-spring 
areas,  are  included  in  table  4.  All  are  characterized  by  the  metals  commonly 
occurring  in  rocks,  of  which  aluminum  is  the  principal  one,  as  contrasted  with  the 
salts  dissolved  in  the  spring  waters,  where  aluminum  is  usually  almost  entirely 
lacking.  Of  the  acid  radicals  present  sulphate  is  predominant  in  every  case  and  is 
exclusively  found  in  the  salts  from  the  hot-spring  areas.  The  salts  from  within  the 
crater  of  Lassen  Peak  contain  a  decided  quantity  of  chloride,  while  Nos.  51  and  52 
from  the  vicinity  of  the  large  fumarole,  though  chiefly  sulphates,  are,  as  we  have 
seen,  remarkable  for  the  presence  of  a  notable  amount  of  pentathionate. 

MICROSCOPIC  EXAMINATION.  > 

A  number  of  the  salts  were  examined  microscopically.  By  means  of  the  optical 
constants  and  the  chemical  composition  together,  it  was  possible  to  identify  a  num¬ 
ber  of  the  minerals  present. 

No.  61  consisted  largely  of  halotrichite  FeS04.Al2(S04)3.24H20  in  fibrous  forms  with  lesser  amounts  of 
voltaite,  a  hydrous  potassium  ferroso-ferric  sulphate  of  undetermined  formula,  and  alunogen 
A12(S04)3.i8H20.  The  sample  also  contained  considerable  material  too  fine  to  identify. 

No.  26  contained  considerable  halotrichite,  with  some  voltaite  and  alunogen. 

No.  52  is  largely  alunogen;  it  also  contains  pickeringite,  MgS04.Al2(S04)3.22H20,  but  no  voltaite1  2. 

No.  51  consists  of  halotrichite  or  pickeringite  (the  optical  properties  are  nearly  identical)  and  very 
little  else.  In  neither  No.  51  nor  No.  52  could  any  material  be  detected  with  a  refractive 
index  as  high  as  that  of  any  known  thionate.  The  substance  which  was  detected  by  chemical 
analysis  was  therefore  presumably  present  in  syrupy  films  spread  over  the  surface  of  other 
crystals.  Halotrichite  and  alunogen  have  been  reported  by  Hague3  from  the  neighborhood 
of  certain  acid  springs  in  the  Yellowstone  Park. 

1  By  H.  E.  Merwin. 

2  The  formulae  are  taken  from  Dana’s  Mineralogy. 

3  Arnold  Hague,  Origin  of  thermal  waters  of  the  Yellowstone  Park,  Bull.  Geol.  Soc.  Amer.,  22,  116,  1911. 


119 


The  Sediments.1 

All  the  springs  contain  more  or  less  mud,  which  varies  from  the  finest  sediment 
to  coarse  fragments  of  altered  lava  in  process  of  disintegration.  Where  the  springs 
have  an  outlet  much  of  the  finest  material  is  naturally  carried  away  by  flowing 
water,  but  where  conditions  favor  its  retention,  as  they  do  in  the  mud  pots,  the 
chief  constituent  of  the  sediment  is  kaolin.  The  few  cases  where  precipitated 
sulphur  was  abundant  form  the  only  exception  to  this  rule  which  has  been  observed 
by  the  authors.  On  the  bottoms  of  some  springs  was  found  a  segregation  of  the 
heavier  and  more  coarsely  crystallized  minerals,  especially  residual  magnetite, 
pyrite  new  and  old,  and  possibly  residual  quartz.  Perhaps  a  more  thorough 
dredging  would  reveal  a  certain  amount  of  segregation  everywhere  in  the  lowest 
layers  of  the  sediments,  but  the  conspicuous  examples  of  it  thus  far  observed  have 
been  in  springs  where  sorting  seems  to  have  been  favored  by  flowing  water.  The 
sediments  are  colored,  according  to  the  minerals  they  contain,  gray,  black,  yellow, 
and  rarely  brown  or  white. 

The  glassy  and  fine-grained  ground-mass  of  the  rock  fragments  is  often  thor¬ 
oughly  altered,  while  magnetite  grains  and  quartz,  feldspar,  and  pyroxene  pheno- 
crysts  are  still  fresh.  These  altered  ground-masses 
contain  widely  varying  proportions  of  kaolin,  opal, 
alunite,  and  pyrite. 

Opal  was  found  in  every  sediment  examined.  Usually  it 
appeared  intimately  aggregated  with  kaolin,  etc.,  but  in  some 
instances  (Bumpass  Hell)  it  was  found  in  small  separate  grains. 

In  a  few  springs,  as  at  No.  5  (Devil’s  Kitchen)  and  No.  6  (Boiling 
Lake),  many  small,  well  faceted,  doubly-terminated  quartz  crystals 
were  present.  It  could  not  be  determined  whether  they  were 
derived  from  the  surrounding  rocks  or  were  a  product  of  the 
thermal  waters. 

The  chief  constituent  of  the  sediment  of  nearly  all  the  springs 
is  a  clay-like  material,  kaolin,  which  may  consist  of  one  or  all 
of  the  recognized  clay  minerals,  kaolinite  (AhO3.2SiO2.2H2O), 
halloysite,  or  leverrierite.  The  mud  ol  Boiling  Lake  is  of  the  same 
character. 

Some  years  ago  a  sample  of  this  mud  was  collected 
by  J.  S.  Diller  and  analyzed  in  the  laboratory  of  the 
U.  S.  Geological  Survey2  by  W.  C.  Wheeler.  This 
analysis,  cited  in  table  5,  shows  that  the  mud  ap¬ 
proaches  kaolinite  in  composition;  the  differences  are 
satisfactorily  accounted  for  by  the  admixture  of  small 
amounts  of  opal  and  rock  debris. 

In  general,  the  kaolin  is  in  the  aggregates  already  described,  as  though  it  had  been  formed 
in  place  during  the  alteration  of  rock  ground-mass  or  feldspar.  The  thoroughly  air-dried  clay  varies 
considerably  in  optical  properties.  It  usually  possesses  an  indefinite  birefringence,  and  refractive 
index  measurements  vary  from  1.5 1  to  1.56. 

1  All  the  microscopic  work  was  done  by  H.  E.  Merwin. 

2  Private  communication  from  George  Steiger,  chief  chemist. 


Iable  5. — Mud  from  Lake 
Tartarus,  California. 


[Analysis  by  W.  C.  Wheeler.] 


Found. 

Cal.  for 
kaolinite. 

SiO, . 

47.51 

46.5 

A  l(), . 

34.08 

39.5 

FeA . 

1.17 

FeO . 

.52 

MgO . 

.28. 

CaO . 

.08 

Na..O . 

.21 

KoO . 

.11 

H20- . 

1  89  13  49 

14.0 

H>0+ . 

11.60/ 

TiO, . 

.65 

ZrOa . 

.09 

PA . 

.81 

S . 

.63 

MnO 

tr. 

BaO . 

.05 

SrO . 

not  det. 

l.i,0 . 

tr. 

99.68 

100.0 

120 


Alunite,  K2O.3Al2O3.4SiO2.6H2O,  in  small  rhombohedra  was  found  in  many  of  the  sediments. 
Generally  it  occurs  in  very  small  quantities.  More  was  found  in  certain  springs  of  Bumpass 
Hell,  but  the  amount  was  nowhere  considerable. 

Sulphur. — Some  springs,  more  especially  certain  ones  in  Bumpass  Hell,  contain 
much  precipitated  sulphur,  imparting  to  the  sediment  a  yellow  color  which  is  some¬ 
times  very  decided.  No.  4,  Bumpass  Hell  (fig.  52),  is  the  most  conspicuous  spring 
of  this  character.  A  sample  of  the  water  was  collected  in  1916,  but  the  sediment 
was  not  so  carefully  examined  as  that  of  a  sample  more  recently  collected  by  J.  S. 
Diller  (1921).  The  latter  sample  contained  about  96  grams  of  sediment  per  liter, 
having  approximately  the  composition1  64  per  cent  sulphur,  17.6  per  cent  opal,  15 
per  cent  kaolin,  3.3  per  cent  alunite,  and  a  very  little  pyrite. 


Fig.  60. — July,  1923.  A  warm  pool  in  the  Devil’s  Kitchen  near  No.  10,  Fig. 

47.  On  the  surface  floated  a  black  scum  of  finely  divided 
pyrite.  Photo  Day. 

Small  amounts  of  sulphur  occur  in  many  pools  and  streams  of  the  hot-spring 
areas  (figs.  61,  62).  A  very  little  is  found  in  the  mud  of  the  Boiling  Lake,  and  in 
the  upper  end  of  the  DeviPs  Kitchen  (south  side)  it  may  be  seen  depositing  on 
rocks  and  banks.  The  fumaroles  of  Bumpass  Hell  are  often  lined  with  needles  of 
sulphur,  and  the  same  was  true  of  the  cracks  along  the  eastern  rim  of  the  crater  of 
Lassen  Peak  not  long  after  the  eruptions,  but  with  the  complete  extinction  of 
fumarole  activity  there  the  sulphur  has  disappeared.  The  crystals  were  always 
orthorhombic.  At  one  time  the  hypothesis  that  some  of  this  sulphur  was  a  primary 
volcanic  emanation  proved  appealing,  but  more  careful  observations  have  made  this 
quite  improbable,  for  it  never  appears  where  its  presence  can  not  be  easily  ac¬ 
counted  for  as  an  oxidation  product  of  hydrogen  sulphide;  and  furthermore,  in  the 
collection  of  gases  from  many  fumaroles,  sulphur  was  never  noticed  as  a  condensa- 


1  Based  on  microscopic  examination  and  several  chemical  determinations. 


121 


tion  product,  as  it  should  be  if  it  were  a  constituent  of  the  gases.  At  the  Sulphur 
Banks,  Hawaii,  where  the  gases  have  a  temperature  of  about  96°,  the  water  con¬ 
densed  from  them  resembles  milk,  though  the  sulphur  vapor  forms  but  a  few 
thousandths  of  1  per  cent  of  the  total  volume  of  the  gases. 


Fig.  61. — July,  1923.  Another  view  of  sulphur  cauldron  (Fig.  52),  at 
Bumpass  Hell.  Greater  gas  evolution  with  lower  water 
level  (no  outlet)  and  higher  temperature.  Photo  Day. 

Fig.  62. — July,  1923.  A  group  of  quiet  sulphur  pools  (Fig.  50,  No.  15) 

Bumpass  Hell.  Photo  Day. 

Pyrite  is  very  generally  distributed  at  the  Geyser,  Boiling  Lake,  Devil’s  Kit¬ 
chen,  and  Bumpass  Hell;  elsewhere  it  has  not  been  sought  for.  It  was  first  found 
in  1915  in  the  mud  at  the  outlet  of  the  Boiling  Lake.  The  next  year,  when  a  more 


122 


careful  survey  of  the  region  was  made,  pyrite  was  found  in  practically  all  the  hot 
springs  and  mud  pots,  but  it  was  most  noticeable  in  the  beds  of  the  little  streams 
which  form  the  outlets  of  the  springs  (fig.  63).  The  amount  of  the  mineral,  how¬ 
ever,  was  so  small  and  the  crystals  generally  were  so  minute  that  it  might  easily 
have  been  overlooked  by  an  observer  intent  upon  the  larger  features  of  the  district. 

Some  of  the  pyrite  was  so  coarse  or  so  characteristic  in  color  as  to  leave  little 
doubt  of  its  identity  in  the  mind  of  a  close  observer,  but  much  of  it  was  too  fine¬ 
grained  to  be  recognized  by  the  unaided  eye.  One  of  the  most  interesting  occurrences 


Fig.  63. — May  20,  1916.  Stream  in  Devil’s  Kitchen  showing  pyrite  crystals  (dark  areas) 
in  furrows  on  the  sandy  bottom  (looking  down  through  the  water).  Photo  Day. 


of  it  was  in  the  form  of  dark  scums  on  the  surface  of  certain  hot,  quiet  pools  (e.  g., 
No.  9,  Devil’s  Kitchen,  and  No.  6,  Bumpass  Hell),  where  in  reflected  sunlight  it 
appeared  as  beautiful  mirrors  of  brass-yellow  color  (figs.  60  and  64).  It  is  easy  to 
get  such  a  mirror  by  boiling  finely  ground  pyrite  in  a  vessel  of  water  (phenomenon 
of  flotation),  and  the  color  of  the  mirror  is  distinctly  different  Irom  a  similar  mirror 
of  marcasite. 

The  black  and  gray  muds  ol  many  springs  had  been  suspected  to  be  colored  by 
pyrite,  but  only  the  microscope  was  competent  to  decide  the  question.  Dispersed 
through  these  sediments  were  found  minute  aggregates  of  an  opaque,  lustrous 


123 


mineral,  from  o.oi  to  0.03  mm.  in  diameter,  which,  from  their  association  with 
larger  aggregates  and  separate  crystals  of  pyrite,  permitted  the  conclusion  that 
they  also  were  pyrite.  The  sediment  contained  no  other  material  which  could  have 
imparted  to  it  a  gray  or  black  color. 

COLLECTION  OF  THE  GASES. 


The  gases  were  collected  over  the  hot  spring  water  in  a  glass  tube  with  the 
upper  end  closed,  the  lower  attached  to  a  glass  funnel.  There  are  some  details 
about  the  apparatus  which  are  perhaps  worth  noting,  since  by  their  application 


Fig.  64. — July  2,  1913.  Hot  pools  in  the  Devil’s  Kitchen  (No.  9,  Fig.  47)  showing  scums  of 
pyrite  reflecting  light  like  bronze  mirrors.  Photo  Day. 


air  is  effectively  excluded  and  gases  may  be  collected  from  difficultly  accessible 
spots.  The  collecting  tubes  were  half-liter  cylinders,  about  40  cm.  long  and  4.3 
cm.  outside  diameter.  The  cylinders  at  each  end  were  drawn  down  to  tips  about 
9  mm.  outside  diameter,  one  tip  closed,  the  other  open.  To  the  open  tip  the  funnel  is 
attached  by  heavy-walled  rubber  tubing  securely  wired.  A  10-cm.  funnel  with 
stem  cut  down  to  a  length  of  about  3  cm.  is  quite  satisfactory.  The  collecting  tube 
is  conveniently  handled  by  a  clamp  attached  to  a  light  pole,  which  carries  the  line 
for  releasing  the  catch  (described  below)  and  another  line  for  holding  the  funnel 
upright  after  filling  the  apparatus  with  water  and  during  the  operation  of  lowering 
it  into  the  pool.  By  using  a  jointed  pole  its  reach  may  be  extended  so  as  to  collect 
gas  in  otherwise  inaccessible  places  (figs.  65,  66). 


124 


To  prevent  any  access  of  air  after  the  tube  is  filled  with  gas  and  before  it  is 
removed  from  the  water,  the  rubber  connection  between  tube  and  funnel  is  tightly 
closed  by  a  strong  spring  clamp,  specially  devised  for  the  purpose.  The  clamp  is 
slipped  over  the  connection  and  fastened  to  the  collecting  tube  before  the  funnel  is 
attached.  The  jaws  of  the  clamp  are  held  open  by  a  catch  while  the  tube  is  filling 
and  closed  at  the  end  of  the  operation  by  simply  releasing  the  spring  catch  with  a 
cord.  The  funnel  may  then  be  safely  detached  and  the  rubber  connection  filled 
with  water,  most  of  which  is  immediately  displaced  by  pushing  in  a  glass  plug. 
The  plug  is  carefully  wired  in  and  the  tube  sealed  off  after  reaching  the  camp. 


Fig.  65. — June,  1922.  Collecting  gases  at  Bumpass  Hell.  Spring  14, 
Fig.  50.  Photo  Day. 


If  the  water  of  a  spring  is  not  too  muddy  it  is  naturally  best  to  use  it  in  filling 
the  apparatus;  otherwise  any  convenient  hot  water  may  be  taken.  Gas  solubility 
counts  for  little  in  waters  near  the  boiling-point.  To  collect  gases  from  mud  pots 
is  not  quite  so  easy.  Where  the  mud  is  thick  the  funnel  must  be  held  in  position  or 
it  will  rise  and  let  in  air.  In  one  case  where  the  mud  was  very  thick  the  tip  of  the 
collecting  tube  was  completely  clogged  by  it  and  collection  proved  impossible. 
Several  gallons  of  water  were  therefore  poured  into  the  pot  and  left  to  stand  some 
hours  till  the  water  was  hot;  collection  then  proceeded  without  trouble.  A  little 
care  is  required  in  sealing  a  tube  filled  from  a  mud  pot,  because  the  tip  is  sure  to  be 
smeared  with  mud,  but  if  the  operator  works  slowly  the  mud  dries  out  gradually, 
and  the  sealed  joint  will  not  crack. 

ANALYSIS  OF  THE  GASES. 

Samples  of  volcanic  gases  for  analysis  have  usually  been  transferred  from  the 
collecting  tube  to  the  measuring  burette,  saturated  with  moisture  as  they  occur  in 
the  field.  To  what  extent  the  results  are  affected  by  this  procedure  when  the  gases 
contain  hydrogen  sulphide,  as  those  from  Lassen  Park  usually  do,  has  never  been 


125 


ascertained,  but  the  mercury  is  blackened  and  the  measuring  burette  fouled  by  it. 
To  avoid  the  error  so  caused,  the  gases  under  discussion  were  pumped  through 
an  ample  supply  of  phosphorus  pentoxide  and  measured  dry  l.  The  hydrogen 
sulphide  was  then  absorbed  by  lead  dioxide.  The  residual  gas  was  subsequently 
transferred  to  a  burette  containing  a  drop  of  water  and  was  measured  again  in  the 
saturated  state.  The  difference  between  the  two  volumes,  when  reduced  to  stand¬ 
ard  conditions,  is  obviously  the  volume  of  the  hydrogen  sulphide.  The  subsequent 
operations  of  analysis  can  then  be  carried  out  with  absorbent  solutions  instead  of 
dry  absorbents  and  much  time  saved  thereby.  By  pumping  out  the  contents  of  the 
collecting  tube  through  phosphorus  pentoxide  (one  bulb  of  which  is  renewed  after 
each  operation),  the  soluble  gases,  which  would  otherwise  be  partly  retained  in  the 


Fig.  66. — June,  1923.  Collecting  gases  at  the  mud  springs  of  Boiling  Lake.  Photo  Day. 

water  which  wets  the  inside  of  the  tube,  may  he  completely  removed.  In  practice 
the  tip  of  the  tube  is  connected  to  the  drier  by  cementing  each  to  the  ends  of  a 
crushing-screw  which  is  immersed  in  mercury  (fig.  67).  The  tip  can  thus  be  broken 
without  access  of  air.  The  method  has  been  employed  by  E.  S.  Shepherd  for  volcanic 
gases,  but  as  his  samples  contained  no  hydrogen  sulphide  the  subsequent  procedure 
was  necessarily  different.  To  avoid  any  reaction  with  moist  hydrogen  sulphide, 
the  steel  crushing-screw  was  plated  with  platinum.  The  gases  were  first  pumped 
into  a  dry  burette,  the  mercury  of  which  was  carefully  protected  from  the  moisture 
of  the  outside  air  (fig.  69).  About  95  c.  c.  was  usually  taken  for  analysis.  After 
volume,  temperature,  and  pressure  had  been  measured,  the  gas  was  transferred  to  a 

1  Dried  gases  containing  hydrogen  sulphide  up  to  about  9  per  cent  have  been  stored  over  mercury  for  days  and  no  decom¬ 
position  within  the  limits  of  error  has  ever  been  noticed.  Slight  blackening  is  sometimes  seen.  Whether  or  not  this  is  due 
to  a  trace  of  moisture  has  not  been  ascertained.  These  observations  apply  to  periods  of  a  few  days  up  to  a  week  or  two  with 
smaller  amounts  of  hydrogen  sulphide. 


126 


67  68 

Fig.  67. — Device  for  removing  the  gas  from  the  collecting  tube.  Photo  Snapp. 
Fig.  68. — Pipette  for  absorbing  hydrogen  sulphide.  Photo  Snapp. 


1  The  cylindrical  pellet,  8  mm.  in  diameter  by  5  mm.  in  thickness,  was  made  by  compressing  the  powder  (free  from  PbO) 
with  a  drop  of  water  at  a  pressure  of  2,000  kg.  At  first  the  pellets  were  moistened  with  phosphoric  acid,  but  this  is  un¬ 
necessary  under  our  conditions  and  it  fouls  the  mercury  somewhat.  Other  investigators  have  used  for  the  absorption  of 
hydrogen  sulphide  balls  of  manganese  dioxide  or  lead  dioxide  made  up  with  oil  and  moistened  with  phosphoric  acid.  Accord¬ 
ing  to  Bunsen,  who  was  apparently  the  first  to  use  the  method,  the  ball,  if  not  properly  made,  will  absorb  more  indifferent  gas 
than  the  amount  of  the  hydrogen  sulphide  present. 

See  Bunsen,  GasometrischeMethoden.  Braunschweig  1877  P-  m>  Christensen,  Tiddskr.  Phys.  and  Chem.,  28,  226,  1889; 
Thorkelsson,  Memoires  de  I’Academie  royale  des  Sciences  et  Lettres  de  Danemark,  8,  181,  1910. 


mercury  pipette  containing  a  pellet  of  lead  dioxide.1  1  he  pellet  was  attached 
to  a  platinum  wire,  the  lower  end  of  which  formed  a  spring.  When  pellet  and  wire 
are  pushed  through  the  inlet  tube  of  the  pipette  the  spring  is  capable  of  holding  the 
wire  and  pellet  in  any  desired  position.  I  he  leveling-bulb  is  then  attached  and 
securely  wired  to  the  inlet  tube  and  the  mercury  is  introduced  (fig.  68). 


127 


If  the  pellet  is  floated  on  the  mercury  it  of  course  rises  to  the  top  when  the  gas 
is  driven  out  of  the  pipette  and  retains  a  little  gas  clinging  to  its  surface.  This  gas 
is  difficult  to  dislodge,  but  when  the  wire  is  used  the  air  is  easily  detached  by  the 
simple  expedient  of  squeezing  the  rubber  tube  and  thus  agitating  the  mercury. 
It  is  wise  to  use  a  Iresh  pellet  for  every  determination  of  hydrogen  sulphide,  since 
the  surface  becomes  coated  with  the  reaction  products  and  with  a  film  of  mercury. 
It  seems  to  be  a  limitation  of  the  method  that  a  pellet  dense  enough  to  prevent 
absorption  of  other  gases  will  not  absorb  a  great  deal  of  hydrogen  sulphide.  If  the 
hydrogen  sulphide  is  large  in  amount  there  would  be  no  objection  to  using  two 


Fig.  69. — Apparatus  for  analysis  of  gases.  ‘  ‘Dry  ’’  burette  at  left.  Apparatus  for  removal 
of  nitrogen  from  the  inert  gases  in  the  foreground.  Photo  Snapp. 

pellets  at  once.  The  hydrogen  sulphide  is  rather  rapidly  absorbed  and  experiments 
proved  that  the  absorption  is  complete.  After  an  hour  the  residual  gas  is  transfer¬ 
red  to  the  “wet”  burette  and  measured  again,  together  with  temperature  and 
pressure.  Perhaps  it  is  hardly  necessary  to  say  the  burettes  were  both  filled  with 
mercury  and  water-jacketed.  The  gases  were  transferred  in  both  cases  through  a 
capillary  connection  which  was  first  exhausted  and  filled  with  mercury,  so  that  no 
gas  was  lost  and  no  air  gained.  No  appreciable  amount  of  carbon  dioxide,  nitrogen, 
or  oxygen,  and  probably  no  other  gas  present  except  the  sulphur  gases,  is  absorbed 


128 


Fig.  70. — Apparatus  for  analysis  of  gases.  ‘‘Moist”  burette,  absorption 
pipettes  and  combustion  pipette.  Photo  Snapp. 

and  3.92  per  cent  H2S  was  found.  In  a  second  mixture  of  the  same  gases  the  results 
were  8.94,  8.88,  8.84,  and  9.15  per  cent. 

I  he  “wet”  burette  was  connected  on  the  one  hand  to  a  compensator  and  on  the 
other  to  an  apparatus  specially  constructed  on  the  Orsat  principle,  the  pipettes  of 


by  the  compressed  pellet,  but  there  was  a  constant  error  of  about  0.3  c.  c.,  not  yet 
accounted  for,  involved  in  the  transfer  of  gas  from  one  burette  to  the  other,  whether 
the  pellet  is  present  or  not.  When  this  error  is  corrected  the  results  are  good. 
Thus  in  a  synthetic  mixture  of  hydrogen  sulphide  and  caibon  dioxide  3.84  per  cent 


129 


which  were  joined  to  a  “manifold”  made  from  a  capillary  i  mm.  in  inside  diameter. 
The  connections  to  the  burette  were  made  with  Khotinsky  cement,  insuring  ab¬ 
solutely  tight  joints  without  too  much  rigidity.  The  pipettes  were  also  sealed  to 
the  apparatus  (fig.  70)  in  the  same  way,  thus  permitting  the  ready  renewal  of  the 
reagents.  The  combustion  pipette  1  has  already  been  described.  Perfectly  tight 
stopcocks  intervened  between  each  pipette  and  the  capillary  manifold.  In  practice 
it  is  necessary  to  attach  the  leveling-bulb  of  the  burette  to  a  cage,  which  slides 
vertically  on  a  smooth,  greased  rod  and  which  can  be  clamped  to  the  rod  in  any 
position  and  afterwards  leveled  with  an  adjusting  screw  by  the  aid  of  the  com¬ 
pensator.2 

The  absorbents,  in  order,  were  caustic  potash  for  C02,  alkaline  pyrogallol  for 
Oo,  and  acid  cuprous  chloride  for  CO.  Combustions  were  made  over  mercury  with 
pure  electrolytic  oxygen. 

The  agreement  between  duplicate  analyses  is  all  that  could  be  desired,  the 
differences  in  measurement  ranging  generally  from  o  to  0.1  c.  c.  Criticism  is  often 
made  of  such  gas-absorption  methods  on  theoretical  rather  than  experimental 
grounds,  and  we  are  satisfied  that  when  the  operator  takes  pains  to  displace  each 
gaseous  constituent  from  the  capillaries  and  to  absorb  it  completely  the  errors  are 
very  small. 

For  the  determination  of  the  so-called  rare  gases  the  measured  residue  of 
nitrogen,  etc.,  is  transferred  to  a  mercury  gasholder  which  is  then  sealed  to  an 
exhausted  absorption  apparatus  of  the  usual  type  where  the  gas  is  passed  in  suc¬ 
cession  over  phosphorus  pentoxide,  hot  copper  oxide,  hot  metallic  calcium,  solid 
caustic  potash,  and  phosphorus  pentoxide  again  (fig.  69).  The  gas  is  circulated 
several  times  through  the  train;  finally  the  unabsorbed  gas  is  pumped  into  a  small 
capillary  measuring  tube  carefully  calibrated,  in  which  the  volume  can  be  read  to 
about  0.002  c.  c.  A  spectrogram  of  the  gas  is  then  taken  for  comparison  with 
standards  (fig.  71).  In  the  identification  of  the  rare  gases  the  authors  take  pleasure 
in  acknowledging  their  indebtedness  to  Dr.  E.  G.  Zies,  whose  previous  experience 
made  his  aid  of  great  value. 

Criticism  may  very  properly  be  made  of  the  use  of  an  Orsat  apparatus  for  the 
determination  of  the  rare  gases  if  a  high  degree  of  accuracy  is  required,  for  the 
capillaries  are  filled  before  the  analysis  with  nitrogen,  argon,  etc.,  obtained  by  ab¬ 
sorbing  the  oxygen  (and  C02)  from  a  sample  of  air.  If  the  gas  to  be  analyzed 
contains  nitrogen  and  the  rare  gases  in  proportions  different  from  those  in  the  air, 
it  is  obvious  that  the  residue  tested  for  rare  gases  will  not  contain  them  in  their 
original  proportions.  The  error  increases  of  course  as  the  residue  becomes  smaller 
in  volume  and  as  the  percentage  of  rare  gases  diverges  from  that  in  the  air.  The 
difficulty  can  be  overcome  by  taking  a  second  sample  for  rare  gases  and  removing 
all  other  constituents  by  solid  absorbents  in  an  evacuated  system.  For  reasons 
which  will  appear  presently  the  procedure  was  unnecessary  in  the  present  case. 

1  Allen  and  Zies,  A  chemical  study  of  the  fumaroles  of  the  Katmai  region,  National  Geographic  Soc.,  Contributed  Tech¬ 
nical  Papers,  Katmai  Series,  No.  2,  p.  125,  1923. 

2  When  the  mercury  levels  are  approximately  the  same  before  the  stopcock  of  the  compensator  is  opened,  the  inflow  of 
gas  to  the  compensator  or  outflow  of  air  from  it  is  negligible. 


130 


COMPOSITION  OF  THE  GASES. 

The  gases  are  not  only  all  of  the  same  general  character,  but  they  are  singularly 
constant  in  composition  for  natural  gases.  An  inspection  of  table  6  shows  that 
there  is  a  preponderant  quantity  of  carbon  dioxide  in  every  instance.  The  limiting 
values  for  carbon  dioxide  are  89.8  per  cent  and  96.4  per  cent,  the  average  93.4  per 
cent.  Nitrogen  ranges  from  2.2  per  cent  to  10.2  per  cent,  with  an  average  of  5.5 
per  cent.  Hydrogen  averages  0.60  per  cent,  hydrogen  sulphide  0.60  per  cent, 
and  there  are  traces  of  marsh  gas  and  very  small  amounts  of  oxygen.  The  average 
percentage  of  oxygen  is  o.  10  and  about  one-third  of  the  samples  contain  none  at  all. 


Fig.  71. — Apparatus  for  photographing  spectra  of  the  inert  gases.  Photo  Snapp. 


Many  of  these  results  are  within  the  limits  of  error  of  the  measuring  apparatus 
used  in  the  work  and  are  perhaps  to  be  accounted  for  in  this  way.  It  is  quite  un¬ 
likely  that  oxygen  leaked  into  the  collecting  tube  in  any  part  of  the  process,  nor  is 
oxygen  ever  to  be  regarded  as  a  primary  volcanic  gas.  Its  escape  from  a  hot 
magma  or  batholith  along  with  reducing  constituents  like  the  sulphur  gases  is 
highly  improbable.  There  are,  however,  reasons  for  believing  that  the  oxygen  of 
the  air  becomes  mingled  with  the  volcanic  gases  near  the  surface  of  the  ground, 
indeed,  this  is  much  the  most  satisfactory  way  of  accounting  for  the  sulphuric  acid 
which  is  so  generally  distributed  in  fumarole  regions  (p.  138).  Usually  no  doubt  the 


131 


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No.  24. 1 

Fountain  in 

the  area 

of  recent 

outbreak. 

93° 

89.80 

none 

none 

.20 

.30 

9.00 

.551 

99.85 

No.  9.1 

Hot 

pool  with 

floating 

mirror  of 

pyrite. 

O 

O 

oo 

93.20 

1  95 

none 

.20 

.30 

4.25 

none 

06  66 

No.  1. 

Slightly 
turbid  pool, 
bubbling 
all  over, 
alkaline. 

65° 

90.10 

.45 

.20 

.80 

8.27 

.13 

.10 

100.05 

1.57 

No.  3. 

Hot  spring  in 
clear  pool, 
vigorously 
spouting  at 
times,  alkaline. 

91°  in  1916 

83°  in  1922 

C  ■  O  O  (N  00  o 

Cxi  LO  ■  n  Tt  o  N 

03  vO 

On 

99.95 

1.31 

No.  9 

(East  end.) 

Muddy 

spring 

covered  with 
a  mirror 
of  pyrite. 

O 

to 

Ol 

ON 

93.65 

.25 

.15 

.30 

5 . 70 

none 

LT; 

O 

C: 

O 

No.  11 
(East 
end.) 
Mud 
pot. 

95.65 

.40 

none 

.20 

.25 

3.55 

none 

100.05 

No.  28 
(North  end.) 

Spring 
on  edge 
of  pool 
covered  with 
black  froth. 

o 

▼-H 

O 

95.75 

.35 

none 

.15 

.40 

3.35 

none 

00  001 

No.  27. 

Mud 

pot. 

92.5° 

96.15 

.80 

none 

.15 

none 

2.86 

.04 

none 

100.00 

1.29 

No.  26. 

Pulsating 
spring  in 
bed  of 
hot  steam. 

93.5° 

91.90 

trace 

.... 

.20 

.50 

7.05 

.20 

99.85 

No.  14. 

Hot 
spring 
on  edge 
of  pool. 

O 

CN 

90.20 

.50 

none 

.20 

.90 

8.20 

.05 

100.05 

No.  23. 

Vigorously 
spouting 
spring  in 
hot  pool. 

93° 

92.10 

none 

none 

.20 

.80 

6.51 

.09 

,303 

100.00 

1.43 

No.  18. 

Mud 

pot. 

O 

»o 

GO 

91.70 

.55 

none 

.20 

.45 

7.12 

.08 

none 

100.10 

1.07 

Temper- 
ture  °C. 

G 

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133 


No.  17. 

Very  large 

mud  pot. 

94.70 

.60 

none 

.15 

.95 

3.50 

.05 

.05 

100.00 

1 .31 

No.  16, 
(eastern  end.) 
Slightly  turbid 
pool  in  big 
slumphole. 

96.40 

.50 

.15 

.65 

2.20 

10 

100.00 

No.  14, 
(eastern  pool.) 
Muddy  pool 
heated  by 
spouting  springs. 

90° 

93.70 

40 

none 

15 

1.05 

4.60 

.10 

o 

o 

o 

o 

No.  14, 

(western  pool.) 
Muddy  pool 
heated  by 
spouting  springs. 

91  5° 

93 . 05 
.55 

none 

.20 

.45 

5.38 

.07 

.25 

99.95 

1.31 

No.  12. 

Hot  spring 
within  the 
border  of  a 
hot  pool. 

87.5° 

95.40 

.55 

none 

.15 

.95 

2.90 

.05 

o 

o 

o 

o 

t-H 

No.  10. 

Pool  of  slightly 
turbid  water 
bubbling  over 
whole  surface. 

o 

CO 

O 

93.80 

.60 

none 

.15 

1.20 

3 . 75 

.35 

99.85 

No.  9. 

Spouting  spring, 
muddy. 

88.5° 

94.80 

60 

none 

.15 

1.15 

3.25 

none 

99.95 

No.  4. 

Simmering  pool, 
yellow  with 
precipitated 
sulphur. 

84-85° 

LO  iO  io  o  »o  o 

O  if)  W  h  r<5  CO  C  h 

•  c . 

iO  O  co 

On  G 

100.05 

1.23 

Temperature,  °  C. 

Composition : 

co2 . 

IPS . 

CO . 

ch4 . 

h2 . 

N*> . 

A . 

02 . 

A 

A  +  N2 

c 

Qj 

tJD 

O 

u- 


C 


<L> 


CJ 

c 

cc 


134 


reducing  gases  remain  in  excess,  but  occasionally  an  excess  of  oxygen  may  creep  in. 
Such  a  situation  would  be  most  likely  to  arise  where  the  ground  was  seamed  or 
otherwise  rendered  more  pervious  than  elsewhere.  It  is  a  significant  fact  that 
several  samples  of  gas  collected  by  two  different  persons  along  a  line  of  recent 
subsidence  in  the  Devil’s  Kitchen  should  all  contain  distinctly  more  oxygen  than 
the  average,  namely,  0.3  per  cent  in  sample  No.  23,  0.55  per  cent  in  No.  24,  and 
2.85  per  cent  in  No.  25.  The  analysis  of  No.  25  has  been  omitted  from  table  6. 

From  their  composition  alone  the  gases  might  have  been  adjudged  to  be 
volcanic,1  but  any  possible  doubt  of  the  fact  should  be  dispelled  by  the  circumstances 
of  their  occurrence,  while  the  constancy  of  their  composition  indicates  that  they  are 
all  derived  from  the  same  batholith.  The  gases  exhaled  from  a  magma  in  the  earlier 
stages  of  volcanism  usually  contain  more  carbon  dioxide  than  any  other  gas  except 
steam.  In  the  last  stages  represented  by  these  hot  springs  the  carbon  dioxide 
remains,  while  the  chemically  active  constituents  like  the  sulphur  gases2  and  the 
halogen  acids  have  been  partially  removed  by  reactions  within  the  magma  which 
result  from  falling  temperature,  or  reactions  with  the  mineral  substances  with 
which  they  come  in  contact  on  their  way  to  the  surface.  Any  very  soluble  gases 
like  S02,  HC1,  and  HF  would,  if  originally  present  and  not  otherwise  removed, 
remain  behind  in  the  spring  waters.  Not  until  the  waters  became  alkaline  (p.  164) 
would  the  carbon  dioxide  be  retained  by  formation  of  carbonates  and  bicarbo¬ 
nates,  the  amount  of  it  taken  up  depending  on  the  degree  of  alkalinity  of  the  waters. 
Only  four  alkaline  springs  were  found  in  the  Lassen  district,  and  these  all  con¬ 
tained  very  little  bicarbonate.  Gases  collected  from  two  of  them  were  only  a 
little  below  the  average  in  carbon  dioxide. 


Table  7. 


In  100  parts  of  natural  gas. 

Soffione 

Soffione 

Casotto. 

Tini. 

Sulphuretted  hydrogen . 

2.070 

2.000 

Carbon  dioxide . 

92.800 

92.000 

Methane . 

1.400 

1.900 

Hydrogen . 

2.600 

2.400 

Oxygen . 

0.050 

0.200 

Nitrogen . 

1.048 

1.455 

Argon . 

0.021 

0.029 

Helium . 

0.010 

0.014 

In  the  endeavor  to  reach  an  understanding  of  the  relations  which  volcanic 
emanations  at  various  stages  of  activity  bear  to  one  another,  it  will  be  well  to  cite 
here  the  analyses  of  two  gases  from  the  Larderello  region  in  Tuscany,  by  R.  Nasini 3 
and  his  associates  (table  7).  Although  they  were  collected  from  fumaroles,  which, 

1  For  the  composition  of  volcanic  gases  in  general,  see  F..  T.  Allen,  Chemical  aspects  of  volcanism,  Journ.  Franklin  Inst- 
193,  29-80,  1922.  Appendix. 

Hague  regards  the  gases  from  the  Yellowstone  hot  springs  as  of  surface  origin  (Bull.  Geol.  Soc.  Amer.,  22,  117,  1911). 

2  Bunsen  states  that  the  H2S  in  the  gases  of  Krisuvik  varies  much  more  than  the  C02  because  of  the  chemical  action  of  the 
former  on  the  rocks  of  the  region  {Ann.  chim.  phys.,  38,  266,  1853). 

3 1  soffioni  boraciferi  etc.  Rome,  1906,  p.  82. 


135 


judging  from  the  context  of  Nasini’s  account,  possessed  a  temperature  of  about 
i8o°  C.,  the  gases  bear  a  remarkable  resemblance  to  those  from  the  Lassen  springs, 
differing  chiefly  in  the  somewhat  higher  percentage  of  marsh  gas  and  the  presence 
of  helium. 

Some  of  the  geysers  of  Iceland,1 II. III. IV. V. VI. 1  according  to  Thorkelsson,  are  giving  off  gases 
which  consist  almost  exclusively  of  nitrogen  and  argon.  As  the  waters  of  geysers 
are  almost  invariably  alkaline,  the  original  carbon  dioxide  may  have  been  entirely 
absorbed  and  retained  in  the  water  as  carbonate  and  bicarbonate,  or  partially  trans¬ 
formed  into  other  less  soluble  carbonates  like  those  of  calcium  and  magnesium.  But 
if  so,  what  has  become  of  the  unabsorbed  gases  like  hydrogen  or  marsh  gas,  or  were 
none  of  these  contained  in  the  original  gases?  The  nitrogen  and  argon  are  regarded 
by  Thorkelsson  as  of  atmospheric  origin.  The  solfataric  districts  of  Iceland  give 
off  gases  much  richer  in  hydrogen2  and  hydrogen  sulphide  than  those  of  the  Lassen 
Park,  but  without  a  detailed  knowledge  of  the  Iceland  springs  it  would  be  unwise  to 
venture  any  explanation  of  the  difference. 

Table  8. — Analyses  of  gas  from  the  hot  springs  and  geysers  of  the  Yellowstone 

National  Park. 


[Bv  F.  C.  Phillips.] 


I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

Carbon  dioxide. 

1 .32 

27.88 

18.80 

82.85 

83.69 

44.18 

94.65 

92.57 

98.67 

98.68 

51.74 

77.99 

Oxygen . 

3.50 

6.25 

11.25 

1.53 

1.57 

6.26 

0.60 

1.74 

0.66 

0.06 

3.71 

0.23 

Hydrogen . 

0.10 

0.25 

0.71 

1.82 

0.59 

4.02 

1.10 

0.70 

0 

0.17 

0 

2.16 

Methane . 

0 

3.28 

0 

trace 

3.80 

trace 

0.91 

trace 

0 

0 

0 

0.30 

Hydrogen  sul¬ 
phide  . 

•  0 

0 

0 

0 

0 

0 

0 

0 

0 

0.46 

0 

0.96 

Nitrogen . 

95.08 

62.34 

69.24 

13.80 

10.35 

45.54 

2.74 

4.99 

0.67 

0.63 

44.55 

18.36 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

100.00 

I.  Artemesia  Geyser,  Upper  Geyser  Basin. 

II.  Asta  Spring,  Hillside  Group,  Upper  Geyser  Basin. 

III.  Bottomless  Pit,  Chain  Lake,  Upper  Geyser  Basin. 

IV.  Fissure  Group,  Ebony  Springs,  No.  33,  Lower  Fire- 

hole  Basin. 

V.  Fountain  Geyser,  Lower  Firehole  Basin. 

VI.  Coral  Spring,  Norris  Geyser  Basin. 


VII.  Echinus  Geyser,  Norris  Geyser  Basin. 

VIII.  Cleopatra  Spring,  Mammoth  Hot  Springs. 

IX.  Sulphur  Spring,  Mammoth  Hot  Springs. 

X.  Mammoth  Hot  Springs. 

XI.  Blue  Glass  Spring,  Shoshone  Geyser  Basin. 

XII.  Taurus  Geyser,  Shoshone  Geyser  Basin. 


The  gases  from  some  hot  springs  and  mud  pots  consist  almost  wholly  of  marsh 
gas.  Of  its  origin  we  have  as  yet  but  meager  evidence,  and  must  content  ourselves 
here  with  pointing  out  what  appears  to  be  a  general  rule  and  a  rational  one,  that  the 
preponderant  constituents  of  hot-spring  gases  C02,  N2  +  A,  and  CH4  are  in  the 
chemical  sense  all  comparatively  inactive  at  low  temperatures.  A  decided  excep¬ 
tion  to  the  rule  is  found  in  the  analyses  of  gases  from  the  hot  springs  of  the  Yellow¬ 
stone  Park  by  F.  C.  Phillips  (table  8). 3  Most  of  these  analyses  contain  oxygen  in 

1  Memoires  de  V Academie  royale  des  Sciences  et  Lettres  de  Danemark,  8,  252,  19x0. 

2  See  Thorkelsson’s  tables.  The  hydrogen  in  these  gases  may  have  been  augmented  by  the  action  of  a  part  of  the  hydro¬ 
gen  sulphide  on  the  tin  collecting  tube  used  (op.  cit..  p.  215). 

3  These  analyses,  which  were  found  in  the  archives  of  the  U.  S.  Geological  Survey,  are  published  by  permission  of  the 
Director  of  the  Survey.  They  were  made  in  the  eighties  by  Professor  Phillips  and  would  doubtless  have  appeared  in  Hague’s 
monograph  of  the  Yellowstone  Park  had  he  lived  to  complete  it. 


136 


very  unusual  quantities,  and  one  would  be  inclined  to  suppose  that  air  crept  in 
either  during  the  collection  or  in  the  course  of  the  analysis  of  the  gases.  In  a 
private  communication  to  the  authors  Dr.  Walter  Harvey  Weed,  who  collected 
the  gases,  states  that  the  method  used  was  discussed  with  the  late  Professor  Hallock, 
who  was  interested  in  the  investigation,  and  that  it  was  concluded  by  them  that  no 
air  could  have  gotten  in  during  the  collection.  Except  for  the  oxygen,  many  of 
these  gases  are  strikingly  similar  to  those  from  the  Lassen  district. 

A  larger  body  of  evidence,  carefully  worked  out  on  the  ground,  will  be  needed 
before  it  will  be  possible  to  give  a  complete  account  of  the  changes  through  which 
volcanic  gases  pass  in  the  course  of  their  history. 

Considering  now  the  ratio  of  argon  to  nitrogen  in  the  gases  under  discussion, 
it  was  explained  above  (p.  129)  that  the  method  employed  in  analysis  was  subject  to 
error  when  the  gases  to  be  analyzed  were  related  in  a  different  ratio  from  that  in  the 
atmosphere.  The  results  show  that  the  ratios  are  not  far  from  the  same;  the  aver- 

A 

age  of  the  determinations  for  ,  —  is  1.33,  while  that  in  the  air  is  1.18.  Con- 

s  A  +  N2 

sidering  the  small  quantities  of  gas  (2.2  to  10.2  c.  c.)  taken  for  analysis,  these  differ¬ 
ences  are  believed  to  be  within  the  limits  of  experimental  error. 

Our  conclusion  is  that  the  nitrogen  and  argon  present  are  probably  chiefly  of 
atmospheric  origin.  We  say  chiefly  rather  than  entirely  because  a  portion  of  the 
gas  might  be  magmatic  and  might  contain  a  somewhat  larger  percentage  of  argon, 
while  the  total  amount  in  the  gas  handled  would  be  too  small  to  enable  us  to  settle 
the  point  by  the  method  used. 

Finally,  there  is  another  point  of  importance  not  revealed  by  the  analyses,  but 
legitimately  inferred  from  sound  knowledge.  All  volcanic  gases,  with  few  excep¬ 
tions,  whether  collected  from  molten  lava  or  from  fumaroles,  contain  more  steam 
than  any  other  gas  and,  though  much  of  this  steam  may  be  of  surface  origin,  the 
unaltered  igneous  rocks  when  heated  almost  invariably  give  off  more  steam  than 
all  other  gases  put  together.  It  follows  that  the  gases  which  escape  from  volcanic 
hot  springs  should  also  have  been  accompanied  by  water  in  relatively  large  amount 
when  they  emerged  from  the  batholith  which  originally  contained  them. 


CHAPTER  III. 

CHEMICAL  EFFECTS  OF  THE  HOT  WATERS  AND  GASES 

CHEMICAL  CHANGES  IN  THE  SPRINGS. 

The  character  of  the  spring  sediments,  the  composition  of  the  waters,  the  gases, 
and  the  lavas  1  of  the  region,  when  correlated  with  observations  in  the  field,  con¬ 
stitute  a  very  satisfactory  body  of  evidence  for  the  interpretation  of  certain  chemical 
changes  which  are  in  progress  in  these  springs.  There  are  two  principal  processes. 
The  first  is  the  formation  ol  pyrite. 

Formation  of  Pyrite. 

The  peculiar  feature  in  this  occurrence  of  pyrite  is  the  great  number  of  minute 
detached  crystals  completely  bounded  by  crystal  planes,  not  the  incompletely 
developed  fragments  which  would  be  left  by  the  disintegration  of  a  rocky  matrix 
inclosing  it.  The  Lassen  lavas  sometimes  contain  a  few  scattered  grains  of  pyrite, 
but  not  such  crystals  as  are  found  in  the  springs.  The  latter  could  result  only  from 
the  formation  of  pyrite  from  the  waters  themselves.  The  occurrence  of  the  micro¬ 
scopic  aggregates,  which  occur  in  the  black  sediments  previously  described,  suggests 
a  first  stage  in  the  process.  There  is  another  point  of  almost  equal  weight.  The 
conditions  in  the  springs  are  strikingly  similar  to  those  found  in  the  laboratory  to  be 
essential  to  the  formation  of  pyrite,  namely,  the  coexistence  of  ferrous  salt,  hydrogen 
sulphide,  and  sulphur.2  The  sulphur  is  not  always  observed  in  the  springs,  but 
contact  with  atmospheric  oxygen  is  all  that  is  necessary  for  its  liberation  from 
hydrogen  sulphide.  This  may  take  place  directly  or  through  the  intermediate 
agency  of  ferric  iron: 

(1)  2FeS04  +  H2S04  +  O  =  Fe2(S04)3  +  H20 

(2)  Fe2(S04)3  +  H2S  =  2FeS04  +  H2S04  +  S 

Oxidation  of  some  hydrogen  sulphide  by  the  ferric  iron  in  the  lavas  during  the 
process  of  their  decomposition  by  the  acid  waters,  which  will  be  explained  presently 
(p.  138),  is  also  entirely  probable. 

The  formation  of  pyrite  is  not  to  be  regarded  as  confined  to  the  springs  alone. 
The  presence  of  similar  conditions  below  ground  should  lead  of  course  to  the  same 
results. 

There  is  an  interesting  fact  about  the  pyrite  samples  collected  in  the  hot  springs 
and  hot  streams  to  which  we  wish  to  direct  attention.  The  crystal  forms  in  them 
were  not  distributed  haphazard.  In  some  samples  the  cube  was  developed  almost 
to  the  exclusion  of  other  forms,  in  other  samples  the  octahedron.  The  pyrito- 
hedron  was  also  observed,  but  not  commonly.  The  conditions  which  determine 

1  For  analyses  of  many  lavas  from  Lassen  National  Park,  see  F.  W.  Clarke,  U.  S.  Geol.  Survey  Bull.  419,  139,  1910. 

2  Allen,  Crenshaw,  Johnston  and  Larsen,  Am.  Journ.  Sci.  (4)  33,  169,  1914.  See  also  Amer.  Journ.  Sci.,  38,  371,  1914. 

137 


138 


the  crystal  form  constitute  of  course  a  very  obscure  problem,  but  here  we  have 
pyrite  in  the  making  under  conditions  which  vary  from  place  to  place  sufficiently 
to  determine  what  crystal  form  shall  develop.  It  ought  to  be  possible  for  the  crys- 
tallographer  to  find  out  what  these  differences  are,  or  at  least  to  gain  important 
information  on  the  subject. 

Absence  of  Marcasite. 

Marcasite  has  not  been  found  in  any  of  the  hot-spring  areas  under  discussion. 
In  experiments  made  in  this  Laboratory  several  years  ago1,  some  marcasite  was 
always  found  mixed  with  the  pyrite  when  the  solutions  from  which  the  minerals 
crystallize  were  acid.  The  amount  of  the  marcasite  decreased  with  decreasing 
acidity  and  no  experiments  were  tried  with  a  degree  of  acidity  as  low  as  that  in  these 
natural  waters.  The  conclusion  from  the  laboratory  experiments  was  that  some 
marcasite  is  always  formed  when  the  disulphide  of  iron  crystallizes  from  acid  solu¬ 
tions.  This  now  appears  to  have  been  too  sweeping.  Nevertheless,  marcasite  is 
sometimes  a  product  of  hot-spring  waters.  In  the  Katmai  region,  Alaska,2  mar¬ 
casite  was  found  in  boiling  hot  springs  (temperature  970  to  98°  C)  under  circum¬ 
stances  which  left  no  room  to  doubt  that  it  was  formed  by  the  waters;  it  occurred  in 
thin  botryoidal  crusts  deposited  on  pumiceous  material  in  the  beds  of  the  springs. 
Unfortunately  the  composition  of  the  waters  was  not  ascertained,  but  there  is  good 
reason  to  believe  they  contained  free  acid,  for  the  lumaroles  in  the  vicinity  com¬ 
monly  emitted  hydrochloric  and  hydrofluoric  acids.  So  far  as  its  amount  is  con¬ 
cerned,  pyrite  forms  but  a  very  small  portion  of  the  sediments;  the  importance  of 
its  occurrence  lies  in  the  hearing  which  the  observations  may  have  on  the  conditions 
of  formation  of  a  widely  distributed  mineral. 

Origin  of  Sulphuric  Acid. 

Another  chemical  process  which  is  going  on  in  the  springs  is  of  a  more  general 
character,  involving  the  major  part  of  the  sediment.  This  is  the  decomposition 
of  the  lavas  by  the  hot  waters;  but  before  discussing  that  it  will  he  necessary  to 
consider  the  formation  of  the  sulphuric  acid  which  occurs  as  normal  or  acid  sul¬ 
phates  in  all  the  springs,  without  exception. 

Sulphuric  acid  appears  to  be  an  active  agent  of  decomposition  in  all  solfataric 
areas.  Various  explanations  of  its  origin  have  been  given,  all  of  which  depend  on 
the  oxidation  of  some  sulphur-bearing  substance,  primary  or  secondary.  To  be 
sure,  the  acid  has  been  detected3  in  that  portion  of  fumarole  gases  which  is  absorbed 
by  water,  especially  gases  which  contain  sulphur  dioxide,  but  this  is  almost  cer¬ 
tainly  the  product  of  atmospheric  oxidation.  Whether  it  is  formed  near  the 
surface  of  the  ground  and  carried  along  as  a  spray  or  whether  it  is  the  result  of 
oxidation  in  the  course  of  the  collection  of  the  gas  is  a  matter  of  doubt. 

1  Effect  of  temperature  and  acidity  in  the  formation  of  marcasite  (FeS2)  and  wurtzite  (ZnS);  a  contribution  to  the  genesis 
of  unstable  forms.  E.  T.  Allen,  J.  E.  Crenshaw  and  H.  E.  Merwin.  Am.  Journ.  Sci.  (4),  38,  393,  1914. 

2Allen  and  Zies,  A  chemical  study  of  the  fumaroles  of  the  Katmai  region,  Nat.  Geog.  Soc.,  Contributed  Technical  Papers, 
Katmai  Series,  No.  2,  p.  97,  1923.  1  he  many  deposits  of  fine  disseminated  marcasite  in  the  pumice  of  Lake  Rotorua,  New 

Zealand,  may  also  be  a  product  of  solfataric  action.  (See  Park,  Geology  of  New  Zealand,  p.  178,  1910.) 

3  Journ.  Franklin  Inst.,  193,  29  (Appendix),  1922. 


139 


Park1  attributes  the  sulphuric  acid  and  sulphates  in  the  hot  springs  of  New 
Zealand  to  the  oxidation  of  pyrite.  A  steady  supply  of  acid  from  this  source 
for  a  long  period  of  time  would  demand  a  large  body  of  pyrite.  It  is  conceivable 
that  such  a  body  might  be  formed  during  an  earlier  (fumarole)  stage  of  volcanic 
activity,  and  that  subsequent  oxidation  might  ensue  as  a  result  of  the  waning 
emanation  of  hydrogen  sulphide,  bringing  the  formation  of  pyrite  to  a  close  in  some 
places  and  allowing  access  of  air. 

Bunsen2  regarded  the  sulphates  in  the  Icelandic  hot  springs  as  an  oxidation 
product  of  secondary  sulphur  dioxide  by  air  or  by  ferric  iron.  The  sulphur  dioxide 
was  supposed  to  be  formed  by  the  chemical  action  of  sulphur  vapor  on  the  ferric 
oxide  in  the  basaltic  rocks  of  that  region.  Bunsen’s  hypothesis  does  not  apply 
satisfactorily  to  the  facts  observed  in  the  Lassen  district,  for  sulphurous  acid  is 
never  found  in  the  vicinity  of  the  springs,  while  if  it  were  a  primary  emanation  some 
of  it  ought  surely  to  escape  oxidation  and  make  its  way  to  the  surface. 

Sulphuric  acid,  together  with  hydrogen  sulphide,  may  be  formed  by  the  action 
of  water  on  elementary  sulphur.  At  ioo°  the  action  is  negligible,  for  satisfactory 
determinations  of  the  vapor  pressure  of  sulphur  have  been  made  by  volatilizing  it  in 
a  current  of  steam  at  that  temperature.  At  250°,  and  possibly  as  low  as  200°, 
the  action  is  rapid  enough  to  account  for  such  amounts  of  sulphuric  acid,  free  and 
combined,  as  are  found  in  the  springs  under  discussion.  It  is  doubtful  whether  such 
temperatures  exist  in  this  region  at  depths  accessible  to  ground  water,  but  a  more 
important  objection  to  accepting  the  hypothesis  is  the  conclusion  already  reached 
on  the  basis  of  several  facts  that  sulphur  is  not  a  primary  emanation  here  (p.  120). 
Small  amounts  of  sulphuric  acid  may  arise  here  and  there  in  these  hot-spring  areas 
from  the  oxidation  of  secondary  pyrite,  but  to  account  for  a  continuous  supply  of 
the  acid  for  any  considerable  period  of  time,  the  oxidation  of  hydrogen  sulphide 
constitutes  the  most  probable  explanation,  because  this  gas  is  constantly  escaping 
from  the  springs  and  is  generally  distributed  in  all  the  areas.3 

The  oxidation  may  be  accomplished  either  by  ferric  iron  or  by  air  or  by  both. 
The  oxidation  of  hydrogen  sulphide  to  sulphur  by  either  reagent  is  the  reaction  best 
known  to  the  chemist,  but  oxidation  to  sulphuric  acid  has  also  been  established. 
Stokes4  found  that  hot  dilute  ferric  chloride  oxidized  about  one-third  ol  the  sulphur 
in  hydrogen  sulphide  to  sulphuric  acid.  Experiments  made  in  this  laboratory 
indicate  that  if  the  gas  reacts  with  ferric  oxide  rather  than  ferric  salts,  at  a  tem¬ 
perature  of  140°,  the  sulphur  forms  pyrite  but  no  sulphuric  acid.  In  this  case  some 
preliminary  oxidation  of  the  hydrogen  sulphide  with  air  would  be  necessary  before 
the  formation  of  sulphuric  acid  by  ferric  iron  in  the  silicates  could  proceed.  As 
further  evidence  lor  these  reactions  some  experiments  by  Deville  and  Dumas  may 
be  cited.  Deville5  observed  that  a  mixture  of  hydrogen  sulphide,  steam  and  air, 
corresponding  to  the  gases  of  many  volcanic  fumaroles,  with  rock  fragments,  in  a 

1  Geology  of  New  Zealand,  p.  178,  1910. 

2  Liebig’s  Annalen,  62,  10,  1847;  Ann.  Chim.  Phys.,  38,  272,  1833. 

3  Drake’s  Springs  may  be  an  exception.  No  gases  were  observed  to  escape  from  these  waters  and  the  odor  of  hydrogen 
sulphide  was  not  noticed,  but  more  careful  observations  would  be  needed  to  settle  the  question. 

4  Bull  U.  S.  Geol.  Survey,  186,  p.  19;  see  also  Gmelin-Kraut .  6th  ed.,  I,  pt.  2,  p.  219. 

5  Compt.  rend.,  35,  261,  1852;  Jahresb.  der  Chemie,  p.  919,  1852. 


140 


few  months  formed  sulphates  of  the  alkalies  and  alkaline  earths,  while  Dumas1 
found  that  sulphuric  acid  was  gradually  formed  when  hydrogen  sulphide  and  air 
are  brought  into  contact  with  some  porous  substance  at  40°  to  50°  and  more  rapidly 
at  8o°  to  90°. 

The  evidence  thus  goes  to  prove  that  hydrogen  sulphide  may  be  and  probably 
is  directly  oxidized  to  sulphuric  acid  under  the  conditions  prevailing  in  the  hot- 
spring  basins,  but  not  all  of  it  necessarily  changes  in  this  way.  The  free  sulphur 
often  observed  at  the  surface  of  the  ground  is  most  probably  an  oxidation  product 
of  hydrogen  sulphide  by  the  better-known  reaction  (H2S  +  0  =  H20  +  S),  for  it  is 
commonly  found  where  the  conditions  obviously  favor  oxidation.  Thus  it  was 
noticed  in  several  places  incrusting  rocks  over  which  a  thin  sheet  of  waim  spring 
water  was  flowing  (fig.  72);  it  was  found  in  needle-like  crystals  lining  fumaroles  and 


Fig.  72.  June,  1923.  Sulphur  bearing  pools  at  Supan’s  Springs.  Photo  Day. 


ground  cracks  where  hydrogen  sulphide  was  issuing;  in  fact  wherever  it  occurred 
the  sulphur  was  readily  accounted  for  in  this  way. 

Sulphur,  whatever  its  origin,  doubtless  contributes  its  share  to  the  sulphuric- 
acid  supply,  for  while  stable  in  dry  air,  in  moist  air2  it  slowly  oxidizes.  In  this 
region  the  warmth  of  the  ground  would  of  course  be  a  contributing  factor  to  the 
oxidation. 

Chemical  Decomposition  of  the  Lavas. 

The  chemical  decomposition  of  the  lavas  is  of  interest  in  several  respects;  it 
involves  the  formation  of  kaolin  and  is  intimately  related  to  the  origin  of  the  springs. 
The  foregoing  data  enable  us  to  interpret  the  process  with  comparatively  little 
hvpothesis.  The  active  agents  are  hydrogen  sulphide  and  especially  sulphuric  acid. 
When  sulphuric  acid  decomposes  a  silicate  the  final  products  are  free  silica  and  the 


1  Ann.  chim.  phys.,  18,  502,  1846. 

2  Maly,  Monatshejte  Chem.,  1,  205,  1880;  see  also  Gmelin-Kraut,  7th  ed.,  vol.  I,  pt.  1,  377,  1907. 


141 


sulphates  of  the  metals  contained  in  the  silicate,  and  these  products  are  found  in  all 
the  springs.  With  them  occur  two  other  products  of  intermediate  composition, 
namely,  kaolin  and  alunite.  Kaolin,  AloO3.2SiO2.2H2O,  contains  silica  still  un¬ 
liberated  and  alumina  as  yet  unchanged  to  sulphate.  Alunite,  K2O.3  Al2O3.4SO3.6H2O, 
contains  no  silica,  but  it  requires  more  sulphuric  acid  to  transform  its  bases  into 
normal  sulphates;  it  is  a  basic  sulphate. 

SIGNIFICANCE  OF  THE  OCCURRENCE  OF  KAOLIN. 

Kaolin  is  well  known  to  geologists  as  a  decomposition  product  of  certain  sili¬ 
cates,  especially  plagioclase  feldspars,  by  the  action  of  cold  dilute  sulphuric  acid, 
which  commonly  originates  in  such  situations  from  the  atmospheric  oxidation  of 
pyrite.  In  the  springs  ol  the  Lassen  National  Park  kaolin  is  the  product  of  hot 
dilute  sulphuric  acid  on  the  rock  silicates,  or  some  of  them. 

Lindgren  1  contrasts  the  formation  of  kaolin  with  that  of  sericite,  the  former  as 
a  product  of  cold  descending  waters,  the  latter  as  a  product  of  hot  ascending  waters. 
Observations  in  the  Lassen  region  show  pretty  clearly  that  it  is  not  the  temperature 
nor  the  direction  of  flow,  but  the  chemical  nature  of  the  water  which  is  of  vital  im-. 
portance.  Kaolin  is  the  product  of  acid  waters,  whether  cold  or  hot;  where  sericite 
is  formed  the  waters  are  presumably  alkaline.  When  the  waters  are  acid,  tem¬ 
perature  may  determine  which  of  the  clay  minerals  (kaolinite,  halloysite,  lever- 
rierite)  is  found,  but  some  clay  mineral  not  sericite  is  formed  in  both  cases. 

A  knowledge  of  the  limiting  conditions  which  determine  the  formation  of  the 
different  clay  minerals  would  be  very  useful  in  problems  of  this  character,  but  an 
investigation  of  the  subject  is  at  present  unpromising  on  account  of  the  low  capacity 
for  crystallization  of  these  minerals. 

SIGNIFICANCE  OF  THE  OCCURRENCE  OF  ALUNITE. 

Kaolin,  though  comparatively  refractory,  is  slowly  decomposed  by  hot  sul¬ 
phuric  acid,2  the  final  products  being  silica  and  aluminum  sulphate.  It  would 
therefore  not  be  formed  if  the  concentration  of  the  acid  were  sufficiently  high. 

In  composition  alunite  is  a  connecting  link  between  kaolin  and  aluminum 
sulphate,  but  this  of  course  does  not  necessarily  give  the  key  to  its  formation.  It 
may  follow  kaolin  as  a  product  of  further  action  by  sulphuric  acid,  or  it  may  be  a 
precipitate  subsequent  to  the  formation  of  the  soluble  sulphates.  The  complex 
aggregates  of  alunite  with  opal  and  kaolin  which  are  found  in  the  sediments  suggest 
rather  that  the  three  substances  are  contemporaneous  products  of  the  action  of 
sulphuric  acid  on  feldspars  or  volcanic  glass. 

In  some  places  in  this  district  alunite  has  been  deposited  in  a  comparatively 
pure  state.  Thus,  a  mound  about  15  feet  high,  boi  dering  the  pool  in  the  Devil’s 
Kitchen  marked  No.  1  on  the  map,  consists  of  alunite,  at  least  on  the  surface 
(fig.  73).  J.  S.  Diller  discovered  some  years  ago  considerable  amounts  of  this 
mineral  at  Supan’s  Springs.  At  present  no  explanation  for  its  segregation  can  be 
offered. 


1  Economic  Geology,  io,  89,  1915;  see  also  Mineral  Deposits,  p.  305,  1913. 

2  Alexander  Sabeck,  Chem.  Centralblatt,  p.  779,  1902, 


142 


SILICA  THE  FINAL  RESIDUE  OF  ROCK  DECOMPOSITION. 

With  the  possible  exception  of  Drake’s  Springs,  where  a  copious  vegetable 
growth  conceals  the  ground,  the  lava  in  all  the  hot-spring  areas  has  been  more  or 
less  completely  decomposed  by  chemical  action.  Alteration  has  been  most  complete 
at  Bumpass  Hell,  where  practically  every  foot  of  the  ground  (Plate  12)  has  been 
bleached  and  disintegrated.  A  sample  of  the  product  from  the  surface  of  the  hill 
adjoining  the  area  on  the  southeast  proved  to  be  nearly  pure  opal  with  a  little 
unchanged  quartz  and  pyroxene  (Merwin).  It  contained  94.79  per  cent  Si02, 
3.05  per  cent  H20,  1.18  per  cent  A1203,  etc.,  and  very  small  amounts  of  other  oxides. 
In  the  sample  the  banded  structure  of  what  was  doubtless  originally  lava  could  be 


Fig.  73.  -  June,  1923.  Spouting  Spring  in  the  Devil’s  Kitchen  (No.  3,  Fig.  47). 

White  alunite  mound  in  background  at  the  right.  Photo  Day. 


plainly  seen.  This  silica  is  obviously  an  example  of  lava  decomposition  with  acid, 
and  there  is  no  reason  to  doubt  that  the  acid  has  the  same  origin  as  that  which 
occurs  in  the  springs,  namely,  the  oxidation  of  hydrogen  sulphide  and  secondary 
sulphur  by  atmospheric  oxygen  and  ferric  iron.  This  general  decomposition  implies 
a  wider  distribution  of  gases,  either  past  or  present,  than  the  observer  might  at  first 
suppose.  It  is  quite  probable  that  these  hot  springs  were  preceded  by  a  more 
active  stage  of  volcanism  in  which  hotter  gases  were  emitted  in  greater  volume  than 
now,  and  that  when  the  thermal  activity  declined  it  became  extinct  in  some  places. 
This  is  the  normal  course  of  change  in  fumarole  regions. 

Even  to-day  volcanic  gases  are  probably  slowly  permeating  the  ground  and 
escaping  outside  the  spring  and  fumarole  vents,  for  there  are  numerous  barren  areas 
in  the  spring  basins  that  show  no  visible  sign  of  present  activity  at  the  surface, 
where  steam  and  abnormal  temperatures  are  found  but  a  few  feet  below  it.  Thus, 
in  July  1922  a  temperature  of  940  was  found  only  2  feet  below  the  surface  at  a 


PLATE  12 


July  10,  1915.  Spouting  Spring  (No.  14,  Fig.  50)  at  Bumpass  Hell.  Photo  Day. 


umw 

Of  THfc 


143 


distance  of  130  feet  from  the  Boiling  Lake  (northwest  end)  and  farther  still  from  any 
active  vent.  The  ground  was  bare,  but  no  visible  steam  or  water  was  escaping 
from  it.  Exploration  both  at  the  Boiling  Lake  and  the  Devil’s  Kitchen  revealed 
many  similar  spots.  The  instance  cited  is  unusual  only  in  the  greater  distance  of 
the  place  from  an  active  vent.  If  the  steam  in  these  places  is  volcanic,  or  partly 
volcanic  as  we  conclude,  it  must  be  accompanied  by  other  volcanic  gases,  including 
hydrogen  sulphide.  The  latter  would  become  at  least  partially  oxidized,  forwhere- 
ever  the  gases  find  egress,  air  will  gain  access  unless  the  gases  are  escaping  under 
high  velocity,,  which  is  never  the  case  except  in  well-defined  vents. 

That  the  decomposed  lava  of  the  barren  ground  in  the  hot-spring  basins  has 
gone  chiefly  to  silica,  like  that  at  Bumpass  Hell,  has  been  inferred  from  the  uni¬ 
formity  in  its  appearance.  The  subject  deserves  further  study,  but  there  is  other 
evidence  bearing  on  it.  Thus,  the  salts  which  occur  in  places  on  this  barren  earth 
have  invariably  proved  to  contain  more  alumina  than  any  other  base,  as  do  the 


Fig.  74. — June,  1922.  Western  half  of  pool  No.  14  Bumpass  Hell. 

(Cf.  Plate  12.)  Photo  Day. 


lavas  from  which  the  salts  were  derived.  The  complete  decomposition  of  the  lavas 
by  sulphuric  acid  would  result  in  the  liberation  of  silica  and  the  formation  oPsalts  of 
the  same  character. 

These  salts  are  quite  certainly  not  a  product  of  the  evaporation  of  spring 
waters,  as  was  thought  at  first,  for  most  of  the  springs  contain  hardly  any  alumina. 
Only  the  most  acid  waters,  like  those  of  No.  6  and  No.  14  (Bumpass  Hell,  figs.  65, 
74)  and  No.  5  (Devil’s  Kitchen),  could  yield  such  salts,  and  then  only  on  condition 
that,  through  some  chemical  reaction,  the  acid  hydrogen  in  them  could  be  nearly  all 
replaced  by  an  equivalent  of  aluminum.  There  can  be  little  doubt  that  these  salts 
and  the  decomposition  process  which  gives  rise  to  them  are  the  result  of  fumarole 
action.  An  illuminating  bit  of  evidence  on  the  point  was  found  at  the  Geyser,  where 
an  insignificant  fumarole  was  emerging  from  under  a  rock.  A  highly  aluminous 


144 


salt  mixture  (No.  43,  table  4),  mingled  with  opal  and  rock  debris,  occurred  about 
the  orifice  of  the  fumarole,  but  no  kaolin.  The  salts  collected  on  the  summit  of  Lassen 
Peak,  which  are  of  the  same  character  so  far  as  the  bases  are  concerned,  must  be 
assumed  to  form  by  fumarole  action,  for  there  are  no  hot  springs  there. 

TWO  TYPES  OF  LAVA  DECOMPOSITION  CONTRASTED. 

In  the  Lassen  spring  basins,  therefore,  two  types  of  lava  decomposition  appear 
to  be  in  progress,  the  one  producing  kaolin  and  some  silica  without  aluminum 
sulphate ,  the  other  producing  silica  with  aluminum  sulphate.  In  the  fact  that  kaolin 
is  decomposed  by  strong  sulphuric  acid  into  silica  and  aluminum  sulphate,  the  key  to 
the  difference  is  doubtless  to  be  found.  If  the  acid  forms  in  a  place  where  sufficient 
water  is  percolating,  its  concentration  is  kept  down  to  such  a  value  that  the  decom¬ 
position  of  feldspars,  volcanic  glass,  and  possibly  other  minerals  is  incomplete.  The 
intermediate  and  comparatively  stable  compound  kaolin  results,  and  this,  as  we 
have  seen,  generally  occurs  in  the  springs,  together  with  very  dilute  acid.  It  would 
not  be  surprising  if  the  fine  sticky  mud  of  the  low  and  wetter  portions  of  the  Devil’s 
Kitchen  and  Bumpass  Hell  should  also  prove  to  contain  kaolin,  but  observations 
have  not  been  extended  to  these  points. 

On  the  other  hand,  if  sulphuric  acid  forms  in  nearly  dry  ground  it  will  accu¬ 
mulate  by  progressive  oxidation  of  the  sulphur  gases  and  the  concentration  may 
reach  comparatively  high  values — probably  in  the  form  of  sirupy  films.  It  is 
under  such  conditions  that  this  more  complete  type  of  rock  decomposition  occurs, 
as  field  observations  indicate. 

It  may  be  questioned  by  some  whether  sulphuric  acid  ever  occurs  in  nature 
otherwise  than  in  very  dilute  condition.  Some  mineral  specimens  collected  by  the 
authors  in  a  fumarole  area  of  Sonoma  County,  California,  and  recently  examined 
by  Dr.  Merwin  and  ourselves,  have  an  important  bearing  on  this  point.  One  of 
them  consisted  of  a  lower  hydrate  of  magnesium  sulphate  and  some  free  sulphuric 
acid.  While  the  heptahydrate,  epsom  salt,  is  ordinarily  obtained  from  water,  this 
hydrate  crystallizes  from  a  certain  concentration  of  free  sulphuric  acid.  The  other 
specimen  contained  two  acid  ammonium  sulphates.  The  simpler  one,  NH4HS04, 
will  not  crystallize  from  an  aqueous  solution  containing  less  than  about  30  per  cent 
free  sulphuric  acid.  Mr.  Augustus  Locke  recently  brought  to  this  Laboratory  a 
mine  specimen  from  Arizona  in  which  was  identified  an  acid  ferric  sulphate,  Fe203. 
4SO3 .9H20.  The  salt  occurred  close  to  a  layer  of  pyrite  and  was  undoubtedly 
formed  by  its  oxidation.  The  same  salt  was  obtained  artificially  by  Posnjak  and 
Merwin1  from  solutions  containing  not  less  than  about  45  per  cent  free  sulphuric 
acid.  The  statement  assumes  that  an  equivalent  amount  of  S03  is  in  combination 
with  Fe203  as  Fe2  (S04)3. 

It  should  be  noted  that  the  majority  of  the  salts  collected  in  the  Lassen  Park 
contain  free  sulphuric  acid,  or  are  acid  salts  (table  4).  These  facts  constitute  good 
evidence  that  sulphuric  acid  of  comparatively  high  concentration  may  occur  in 
nature  under  favorable  conditions,  doubtless  for  a  limited  time  and  probably  in 
the  form  of  sirupy  films  in  dry  ground. 


1  Journ.  Amer.  Chem.  Soc.,  44,  1991,  1922. 


145 


These  films  of  acid  and  the  salts  they  form  are  doubtless  washed  down  into 
near-by  springs  or  outlets  in  the  wet  season.  Whether  the  amounts  which  accu¬ 
mulate  at  any  one  time  and  place  are  great  enough  to  change  materially  the  com¬ 
position  of  the  waters  is  a  question.  The  table,  as  has  been  pointed  out,  shows 
water  analyses  which  are  relatively  high  in  acid  and  alumina. 

Formation  of  Pentathionate. 

Pentathionate,  which  was  found  in  the  salts  from  the  eastern  rim  of  the  Lassen 
Crater,  has  been  reported  in  nature  but  once  before;  it  was  discovered  by  McLaurin  1 
in  the  water  of  the  crater  lake  on  White  Island  in  the  Bay  of  Plenty,  New  Zealand. 
Its  formation  at  Lassen  Peak  is  not  entirely  clear,  but  there  is  little  doubt  that  it  is 
the  decomposition  product  of  the  lava  by  the  two  sulphur  gases,  hydrogen  sulphide 
and  sulphur  dioxide.  Both  gases  were  proved  to  occur  there  in  1916,  and  it  is  by 
the  interaction  of  the  two  gases  at  low  temperatures  that  pentathionic  acid  has 
been  prepared.2  Moreover,  no  thionates  were  found  in  the  salts  from  any  other 
locality,  nor  was  any  sulphur  dioxide  found  elsewhere.  The  gases  from  a  large  and 
active  fumarole,  occurring  close  by  the  spot  where  the  salt  sample  was  found,  were 
collected  by  pumping  approximately  100  liters  of  gases  through  an  absorption  train 
filled  with  solid  barium  hydroxide.  The  analysis  was  made  by  E.  S.  Shepherd  on 
the  principle  of  the  difference  in  solubility  between  sulphite  and  sulphide  of  barium; 
that  is,  the  soluble  sulphur  was  reckoned  as  hydrogen  sulphide,  the  insoluble  as 
sulphur  dioxide.  Similar  gases  were  collected  on  the  south  rim  of  the  crater  by 
Shepherd  in  1915.  The  reader  will  note  that  the  analyses  account  only  for  those 
gases  retained  by  the  barium  hydroxide,  which  form  a  very  small  part  of  the  whole, 
but  all  the  sulphur  and  halogen  gases  are  doubtless  included. 


Table  9. — Gases  soluble  in  Ba(OH)2.  Per  cent  by 

volume. 


Fumarole  on  Lassen  Peak,  east  side 
of  crater  of  1914;  collected  in 

June  1916. 

Fumarole  on  south  side  of  old  crater; 
collected  by  E.  S.  Shepherd, 

June  1915. 

CO, . 

0.096 

CO, . 

0 . 040 

SO, . 

.054 

so, . 

.005 

1LS . 

.005 

1!,S . 

.004 

HC1 . 

none 

HF . 

none 

While  the  two  sulphur  gases  react  with  each  other  at  low  temperatures,  there 
is  good  ground  for  assuming  that  they  may  coexist  at  high  temperatures.  The 
gases,  as  they  issued  Irom  the  fumaroles,  had  an  overpowering,  pungent  odor  like 
sulphur  dioxide.  Of  course,  there  was  no  means  of  testing  for  hydrogen  sulphide 
in  its  presence.  If  one  is  inclined  to  be  skeptical  of  the  coexistence  of  the  two  gases 
in  the  same  fumarole,  it  is  at  least  certain  that  hydrogen  sulphide  was  issuing  from 
ground  cracks  close  by,  as  it  was  recognized  by  the  odor  and  by  the  lead-paper  test. 

1  McLaurin,  Proc.  Chem.  Soc.,  27,  10,  191 1 ;  see  Clarke’s  Data  of  Geochemistry,  Bull.  U.  S.  Geol.  Survey,  695,  195,  1920. 

2  Wackenroder,  Liebig  s  Ann.  60,  189,  1846;  Debus,  Liebig’ s  Ann.  244,  76,  1887. 


146 


What  must  remain  unexplained  for  the  present  are  the  conditions  of  temperature, 
etc.,  under  which  the  thionate  was  formed.  At  low  temperatures  in  the  presence  of 
water,  thionic  acid,  as  well  as  much  sulphur,  is  obtained  by  the  commingling  of  the 
gases.  At  ordinary  temperature  the  products  are  supposed  to  be  sulphur  and 
water,  but  possibly  a  certain  amount  of  some  thionic  acid  is  also  formed.  Penta- 
thionates  are  unstable,  but  much  less  so  in  the  presence  of  free  acid.  In  accord 
with  this  fact  sample  No.  52,  which  contained  acid  salts,  showed  no  diminution  in 
the  amount  of  thionate  after  18  months. 

It  will  be  seen  in  table  4  that  these  peculiar  salts  from  Lassen  Peak,  like  those 
from  the  other  localities,  contain  more  sulphate  than  any  other  acid  radical — a 
fact  indicating  that  here  also  oxidation  of  the  sulphur  gases  is  an  important  process 
in  the  genesis  of  the  salts. 

Sulphur  dioxide,  upon  which  the  formation  of  pentathionate  probably  depends, 
has  been  previously  regarded  as  a  product  of  higher  temperatures  than  hydrogen 
sulphide,  as  it  probably  was  at  Lassen  Peak  in  1916.  Bunsen  1  states  that  hydrogen 
sulphide  followed  sulphur  dioxide  in  Iceland  after  the  eruption  of  1845,  but  whether 
this  is  indicative  of  surface  oxidation  of  the  hydrogen  sulphide  in  the  earlier  and 
hotter  stages  of  volcanic  activity,  or  a  change  in  the  nature  of  the  primary  gases, 
remains  unsettled. 

Significance  of  Hydrochloric  Acid  in  the  Crater  Gases. 

Contrasted  with  the  very  slight  amount  of  chlorides  in  the  hot-spring  waters 
and  the  salts  of  the  hot-spring  areas  was  the  occurrence  in  1916  of  salts  rich  in 
chlorine  in  certain  parts  of  the  Lassen  crater.  These  salts,  as  has  been  already 
remarked,  were  quite  obviously  derived  from  volcanic  gases  escaping  from  adjacent 
crevices  in  the  lava  and  responding  to  tests  for  hydrochloric  acid.  The  gases 
possessed  the  characteristic  odor,  reddened  blue  litmus,  and  reacted  with  silver 
nitrate  in  the  usual  way.  The  salts  were  in  all  probability  formed  by  the  reaction 
of  the  acid  and  lava  rather  than  by  sublimation.  Neither  the  salts  nor  the  gases 
were  anywhere  copious.  This  occurrence  was  strictly  confined  to  the  crater;  in 
the  fumaroles  outside  the  rim  from  which  gases  were  taken  (p.  145)  no  hydrochloric 
acid  was  found. 

According  to  Bunsen,  the  evolution  of  hydrochloric  acid  as  a  volcanic  gas  is 
dependent  upon  a  “shallow  hearth/’  2  When  the  hearth  sinks  he  believes  that  the 
acid  reacts  with  the  wall  rock,  forming  non-volatile  compounds.  At  Katmai, 
where  hydrochloric  acid  is  generally  prevalent,  it  occurs  in  larger  quantities  in  the 
hotter  fumaroles  and  almost  dies  out  at  ioo°.3  This  is  probably  a  consequence  of 
the  fixation  of  the  acid  in  the  walls  of  the  fumarole  at  the  lower  temperatures. 

At  first  thought  a  similar  explanation  appeared  to  apply  to  the  distribution  of 
hydrochloric  acid  at  Lassen  Peak.  The  acid  was  found  in  the  gases  of  the  crater, 
where  the  climax  of  activity  and  doubtless  the  hottest  temperatures  were  repre¬ 
sented,  while  chlorides  4  were  not  found  in  the  hot-spring  areas  which  are  typical 

1  Ann.  chim.  phys.,  38,  274,  1853. 

2  Ann.  chim.  phys.,  38,  262,  1853. 

•'Allen  and  Zies,  Nat.  Geog.  Soc.,  Contributed  Technical  Papers,  Katmai  Series,  No.  2,  p.  150.  1923. 

4  For  the  relation  between  chlorides  in  hot-spring  waters  and  magmatic  hydrochloric-acid  gases  see  p.  164  et  seq. 


147 


of  a  declining  stage  of  volcanism.  But  the  facts  as  a  whole  do  not  support  this  view. 
The  fumaroles  on  the  outside  rim  of  the  crater  were  giving  out  hotter  gases  in  1916 
than  the  gases  in  the  crater  where  the  hydrochloric  acid  was  found,  and  in  1922, 
when  the  highest  temperature  in  the  crater  was  790  C.  and  only  the  faintest  wisps 
of  steam  were  discernible,  hydrochloric  acid  could  still  be  detected  in  the  gases. 

The  distribution  of  hydrochloric  acid  at  Lassen  Peak  is  not,  therefore,  well 
accounted  for  by  assumed  temperature  differences  in  the  magma  or  magmas  where 
the  gas  originated,  and  at  the  present  time  there  is  no  satisfactory  explanation  for  it. 


Ca  Na 

Table  10. — The  ratios  and  r  in  the  hot  spring  waters 
}%  Mg  K 


No. 

Ca 

Mg 

Na 

K 

No. 

Ca 

Mg 

Na 

K 

1 . 

0.9 

37 . 

2.9 

5.2 

2 

1.2 

60 . 

0.9 

3.8 

3 . 

1.6 

62 . 

2.1 

[14.] 

13 . 

1.5 

6.4 

63 . 

1.1 

5.5 

15 . 

00 

7.5 

64 . 

OO 

[18  ] 

21 . 

2.0 

4.2 

125 . 

1.0 

5.0 

22 . 

[5.0] 

8.5 

128 . 

1.0 

7.5 

221.  .  . . 

[9.0] 

'7.1 

131 . 

2.3 

5.8 

23 . 

2.1 

6.4 

331 . 

1.2 

8.1 

29 . 

1.4 

7.7 

362 . 

OO 

4.6 

30 . 

1.6 

8.1 

400 . 

2.5 

5.6 

31 . 

1.9 

7.0 

Uniformity  of  Rock  Decomposition. 

The  analytical  determinations  on  the  spring  waters  throw  some  additional  light 

Ca 

on  the  processes  of  rock  decomposition.  The  molecular  ratio  — ■  in  the  waters, 

Mg 

reckoned  from  the  results  in  table  2,  shows  a  rough  approximation  to  constancy 
(See  table  10).  In  three  waters,  15,  64,  and  362,  where  no  magnesium  was  found, 
the  ratios  are  erratic,  and  the  same  is  true  of  two  of  the  alkaline  1  waters,  but  other¬ 
wise  the  variation  for  natural  waters  is  slight.  The  limits  are  0.9  and  2.9. 

Na 

The  —  ratios,  with  two  exceptions,  also  vary  within  comparatively  narrow 
Jk. 

bounds,  namely  from  3.8  to  8.5.  The  exceptional  ratios  belong  to  waters  from 
springs  without  visible  outlet,  in  which  an  unusual  amount  of  potassium  had 
precipitated  as  alunite.  F.  W.  Clarke  2  has  compiled  about  20  analyses  of  dacites 
and  andesites  from  this  region.  From  his  figures,  omitting  one  peculiar  analysis, 

Ca 

we  reckon  the  average  ratio  for  the  dacites  as  1.2  and  the  limits  0.3  and  1.9. 
The  average  ratio  for  the  andesites  is  1.7,  with  1.2  and  2.0  as  the  limiting  values. 


1  Analyses  22  and  221  of  spring  19,  Devil’s  Kitchen  (table  3). 

2  U.  S.  Geol.  Survey.  Bull.,  419,  p.  139.  1910. 


148 


Na 

The  — -  ratio  averages  2.6  in  the  dacites,  with  1.4  and  4.0  as  the  limiting  values, 
K 

while  the  average  for  the  andesites  is  3.6,  with  1.5  and  5.5  as  limiting  values. 

Comparing  the  ratios  deduced  from  the  water  analyses  with  those  deduced 
from  the  rock  analyses,  the  former  are  seen  to  agree  somewhat  better  with  the 

andesite  ratios.  The  ratios  are  remarkably  close;  the  —  ratios  are  higher 

o 

in  the  waters  than  they  are  in  the  andesites,  though  the  difference  between  the 


Fig.  75.  July  2,  1915.  Eastern  end  of  the  Devil’s  Kitchen  showing  encrusted  ground  and 
sulphur  pools.  Photo  Day. 


limits  in  both  cases  is  about  the  same.  The  precipitation  of  potassium  as  alunite  in 
the  waters  would  of  course  raise  the  ratios.  The  amount  of  alunite  in  the  sediments 
is  always  small,  though  more  may  be  precipitated  below  ground. 

The  remarkable  fact  about  these  ratios  is  that  they  approach  as  closely  as  they 
do  to  similar  ratios  in  the  lavas.  This  agreement  does  not  imply  any  uniformity  in 
the  rate  at  which  the  rock  is  decomposed.  Of  course,  the  various  minerals  in  the 
rock  must  decompose  at  different  rates,  and  the  varying  concentration  of  the  salts 
in  the  spring  waters  shows  that  the  acid  concentration  also  must  vary  in  different 


149 


parts  of  the  field.  What  the  results  do  imply  is  that  the  decomposition  process  does 
not  proceed  in  definite  stages,  but  that  fresh  rock  must  be  continually  exposed  to 
chemical  action.  If  the  decomposition  products  kaolin  and  silica  effectually  in- 
crusted  the  surface  of  the  lava,  it  is  obvious  that  the  ratios  would  eventually 
depart  widely  from  those  in  the  original  rock.  It  might  be  expected  that  as  the 
exposed  surface  of  the  more  refractory  minerals,  quartz,  pyrite,  magnetite,  and 
pyroxene,  increases  as  a  result  of  rock  disintegration,  the  ratios  would  undergo  a 
vital  change.  They  piobably  do  change  somewhat.  The  lavas,  however,  are 
tolerably  homogeneous  in  the  mass,  consisting  largely  of  volcanic  glass,  which  is 
rather  rapidly  altered.  Surfaces  of  the  refractory  minerals  also  are  exposed  from 
the  start,  and  the  increase  in  the  surface  exposure  is  apparently  too  small  to  affect 
the  results  vitally. 

While  the  ratios  under  discussion  agree  a  little  better  with  those  in  the  andesites 
than  with  those  in  the  dacites,  these  rocks  are  not  sufficiently  unlike  in  composition 
to  warrant  any  conclusion  as  to  which  of  the  two  supplies  most  of  the  bases  found 
in  the  waters. 


CHAPTER  IV. 


ORIGIN  OF  HOT  SPRINGS  AND  THEIR  RELATION  TO 

IGNEOUS  ACTIVITY. 

SOURCE  OF  HEAT  IN  THE  HOT  SPRING  AREAS. 

Volcanic  Heat. 

The  observations  which  have  been  presented  in  the  foregoing,  in  so  far  as  they 
bear  on  the  origin  of  the  heat  of  the  springs,  may  be  summarized  as  follows:  While 
the  volume  of  hot  water  discharged  from  the  Lassen  hot  springs  is  small,  the  heat- 
supply,  compared  to  the  supply  of  water,  must  be  large,  for  a  great  number  of  the 
springs  are  boiling  hot,  many  are  spouting  jets  of  hot  water  to  heights  of  i  to  3  feet, 
and  a  few  at  times  send  up  jets  to  heights  of  5  or  10  feet  (Plate  7).  Some  fumaroles 
in  the  same  areas  pour  out  considerable  volumes  of  steam.  One  roaring  fumarole  at 
Bumpass  Hell  in  1916  showed  a  maximum  temperature  of  117.50,  though  all  other 
fumaroles  tested  had  a  temperature  about  equal  to  that  of  boiling  water  for  the 
elevation.  The  geologic  observations,  as  we  have  already  found,  show  that  the 
region  is  volcanic,  and  has  been  recently  active,  that  the  spring  areas  were  originally 
covered  with  lava  flows,  and  that  they  are  ranged  along  fault  lines,  while  the 
alignment  of  springs  also  suggests  local  cracks  in  several  areas. 

In  entire  accord  with  these  facts  is  the  almost  universal  occurrence  of  volcanic 
gases  in  the  springs.  The  uniform  character  of  the  gases  throughout  the  region,  so 
far  as  they  have  been  investigated,  is  indicative  of  a  common  source.  That  the 
source  is  a  hot,  underlying  magma  or  batholith  will  hardly  be  questioned  by  a 
student  of  the  subject,  for  all  igneous  rocks,  which  at  an  earlier  period  of  their 
history  were  magmas  themselves,  give  off  similar  gases  when  heated.  While  the 
evidence  all  appears  very  clear  and  consistent,  there  are  some  other  sources  of  heat 
which  should  be  discussed. 

Radioactivity  as  a  Source  of  Heat. 

While  the  radioactivity  of  the  gases  and  waters  of  the  Lassen  springs  has  not 
been  investigated,  tests  of  this  kind  have  been  made  in  Iceland  by  Thorklesson1  and 
in  the  Yellowstone  Park  by  Schlundt  and  Moore2  with  decisive  results.  The 
amount  of  the  emanation  in  both  these  famous  hot-spring  areas  is  considerable;  in 
the  Yellowstone  it  is  as  great  as  that  of  well-known  European  localities,  but  no 
connection  is  found  between  the  amount  of  it  and  the  temperature  of  the  waters. 
In  fact,  the  cold  waters  of  the  Yellowstone  were  slightly  more  radioactive  on  the 
average  than  the  hot  waters.  Thorkelsson  started  out  with  the  hypothesis  that 
the  source  of  the  heat  was  radioactivity,  but  both  he  and  Schlundt  and  Moore  came 
to  the  conclusion  that  radioactivity  had  nothing  to  do  with  it.  As  a  result  of  other 

1  Memoires  de  l’ Academie  royale  des  Sciences  et  Lettres  de  Danemark,  8,  199,  1910. 

2  U.  S.  Geol.  Surv.  Bull.  395,  1909. 


150 


151 


investigations  it  has  not  been  found  that  mineral  deposits  which  are  particularly 
radioactive  are  associated  with  local  high  temperatures.  This  evidence  is  so 
definite  and  conclusive  that  further  investigation  along  the  same  line  appears 
unpromising. 

Heat  Developed  from  Chemical  Processes. 

Some  are  inclined  to  attribute  to  oxidation  or  to  other  chemical  processes, 
which  are  supposed  to  be  in  progress  near  the  surface  of  the  ground,  a  part  or  all  of 
the  heat  supply  of  hot  springs.  In  the  foregoing  (pp.  137,  140)  the  evidence  has  been 
presented  for  two  principal  chemical  processes  occurring  both  in  the  springs  and  also 
presumably  below  ground.  The  most  important  as  regards  the  amount  of  the 
products  is  the  decomposition  of  the  rocks  by  sulphuric  acid.  In  a  general  way  the 
following  expression  may  serve  to  represent  this  process: 

a  Silicates  +  b  sulphuric  acid  =  c  sulphates  +  d  kaolin  +  e  silica 

The  other  product,  alunite,  will  be  for  a  moment  neglected.  This  expression 
is  not  a  true  equation,  for  the  reason  that  a  small  amount  of  water  is  absorbed  from 
outside  the  system  in  the  formation  of  kaolin,  but  the  assumption  that  it  is  an 
equation  is  sufficiently  near  the  truth  for  the  purposes  of  this  calculation.  The 
method  of  calculation  simply  takes  account  of  the  soluble  products  found  in  a  given 
volume  of  hot-spring  water,  from  which  can  be  estimated  approximately  the  quan¬ 
tities  of  the  other  products  involved  in  the  chemical  process  considered.  The 
resulting  equation  is  then  treated  as  a  thermal  equation.  Although  it  is  not 
possible  to  determine  all  the  chemical  coefficients  accurately  and  the  thermal  data 
are  not  entirely  complete,  it  is  quite  possible  to  estimate  the  order  of  magnitude  of 
the  aggregate  heat  effect  satisfactorily. 

We  select  as  an  example  one  of  the  most  favorable  cases,  that  of  a  boiling  spring 
of  the  highest  concentration.  The  soluble  matter  in  a  liter  of  it  consists  of  0.4 
gram  of  sulphates,  equivalent  to  0.15  gram  of  rock  bases  (Na20,  K20,  FeO,  etc.), 
some  free  acid  which  had  not  had  time  to  act  on  the  rock,  and  a  very  little  ammoni¬ 
um  sulphate  which  is  assumed  to  have  been  derived  from  ammonia  in  the  mag¬ 
matic  gases.  Included  in  the  0.15  gram  of  rock  bases  are  a  few  centigrams  of 
alumina,  which  is  usually  very  low  in  these  waters.  For  the  sake  of  simplicity 
we  shall  assume  that  all  the  alumina  in  the  original  rock  is  transformed  into  kaolin. 
At  the  same  time,  to  insure  a  liberal  estimate  of  the  heat  quantity,  the  heat  of 
formation  of  the  aluminum  sulphate  actually  found  will  be  taken  account  of. 

As  to  the  composition  of  the  rock  from  which  these  sulphates  were  derived, 
many  of  the  dacite-andesites,1  the  lavas  in  which  all  the  hot  springs  occur,  have 
been  analyzed.  The  silica  and  alumina  in  them  average  about  60  per  cent  and  17 
per  cent  respectively.  Now,  bearing  in  mind  that  kaolin  contains  aboiFt  40  per 
cent  of  alumina  and  46.5  per  cent  of  silica,  we  have  approximately: 

0.7  gram  silicates  +  0.3  gram  sulphuric  acid  =  0.4  gram  sulphates  +  0.3  gram 

kaolin  +  0.28  gram  silica. 

A _  ..V  *  ...  -j  V _ : _ 

1  F.  W.  Clarke,  U.  S.  Geol.  Surv.,  Bull.  419,  139,  1910. 


152 


The  total  heat  effect  we  have  to  consider  is  the  sum  derived  from  two  pro¬ 
cesses:  the  heat  produced  in  the  decomposition  of  the  rock  as  represented  above, 

and  hit  the  heat  produced  in  the  formation  of  the  acid  which  decomposes  the  rock. 
The  formation  of  the  sulphuric  acid  involves  some  speculation.  In  our  opinion  it  is 
most  probably  formed  by  the  oxidation  of  hydrogen  sulphide  brought  up  in  the 
magmatic  gases.  Whether  it  is  formed  from  hydrogen  sulphide  or  sulphur,  the 
order  of  magnitude  is  the  same  in  both  cases.  This  question  has  already  been 
discussed  in  another  connection  (see  p.  138).  The  total  quantity  of  the  sulphuric 
acid  from  which  the  sulphates  in  the  spring  water  are  derived  is  0.695  gram  per 
liter,  of  which  about  half  in  this  case  remains  undecomposed: 

hi  =  0.695  X  1 .3 8  =  0.96  kg.  cal.,  or  0.695  X  1 .45  =  1.0  kg.  cal., 

where  the  factors  1.38  and  1 .45  are  simply  the  heats  of  formation  in  kilogram  calories 
of  1  gram  of  acid.  We  will  call  hi,  therefore,  1  kg.  cal. 

Some  of  the  thermal  data  required  for  the  calculation  of  h2  are  wanting,  but 
values  have  been  chosen  which  are  within  the  limits  of  probability.  As  a  basis  for 
the  selection  we  have  the  heats  of  formation  of  a  few  synthetic  silicates,  all  of  which 
vary  from  2  to  3  kg.  cal.  per  gram.  Inasmuch  as  heats  of  formation  in  general  have 
similar  limits,  it  is  quite  unlikely  that  the  values  either  for  the  primary  silicates  or 
for  kaolin  are  exceptional.  The  other  data  are  known.  From  these  we  have: 

hi  =  0.7  gram  [silicates]  +  0.3  gram  [sulphuric  acid]  =  0.4  gram  [sulphates]  +  0.3 

gram  [kaolin]  +  0.28  gram  [silica]. 

or  in  kilogram  calories: 

hi  =  —  7  X  2.0  —  0.3  X  2.151  =  0.952  +  0.3  X  3.0  -F  0.28  X  3.0  —  0.6. 
hi  =  0.6  kg.  cal.  hi  +  hi  =  1.6  kg.  cal. 

The  terms  of  this  equation  are  all  of  a  very  small  magnitude  and  the  alteration 
of  any  of  them  or  several  of  them  by  large  percentages  could  not  make  any  im¬ 
portant  change  in  the  magnitude  of  the  result.  Again,  though  no  account  has 
been  taken  of  the  heat  of  formation  of  alunite,  the  amount  of  this  mineral  in  any 
spring  sediment  examined  has  always  proved  slight  as  compared  to  the  kaolin. 

The  temperature  of  the  hot  spring,  the  products  of  which  are  under  discussion, 
was  about  910  C.  If  the  temperature  of  the  ground  water  is  taken  as  io°  C.,  it  is 
obvious  that  the  aggregate  heat  effect  from  the  processes  considered  would  be 

-  — ,  or  about  2  per  cent  of  the  heat  required  to  raise  the  temperature  of  the  ground 
8 1 

water  to  boiling.  In  this  discussion  we  have  taken  one  of  the  most  favorable 
cases.  In  most  springs  the  mineral  content  is  much  smaller  and  the  corresponding 
heat  effect  therefore  much  less. 

The  rate  of  rock  decomposition,  as  we  view  the  matter,  is  not  rapid  enough  to 
yield  a  heavily  mineralized  water  nor  any  considerable  portion  of  the  heat.  If  it  is 
contended  that  there  may  be  other  chemical  processes  which  have  been  left  out  of 

1  The  equation  of  course  involves  the  heat  of  formation  of  sulphuric  acid  from  the  elements.  This  is  somewhat  greater 
than  the  heat  effect  of  the  oxidation  of  the  sulphur  gases,  H2S;  or  S8. 

2  This  figure  includes  a  small  heat  effect  from  the  neutralization  of  ammonia. 


153 


discussion,  we  can  only  say  there  are  none  of  which  we  have  evidence  which  could 
contribute  any  important  quantity  of  heat.  There  is  the  formation  of  pyrite, 
but  the  amount  of  it  in  the  sediments  is  too  small  to  have  any  important  bearing  on 
the  problem  in  hand. 

If  we  assume  that  mineral  veins  are  in  process  of  formation  in  the  conduits, 
through  which  the  volcanic  gases  ascend,  we  must  admit  that  the  rate  of  formation, 
judging  by  what  is  known  of  geological  processes  in  general,  is  probably  fully  as 
slow  as  the  decomposition  processes  we  have  discussed. 


Fig.  76. — July  2,  1915.  Western  end  of  the  Devil’s  Kitchen  close  to  Warner  Creek.  Steam 
indicates  the  location  of  hot  springs.  Photo  Day. 

It  is  therefore  concluded  that  chemical  reactions,  not  only  those  in  progress 
near  the  surface  of  the  ground,  but  any  which  may  be  in  progress  in  the  zone  of 
deposition,  are  a  minor  factor  in  supplying  heat;  for  the  major  part  we  must  go  back 
to  the  original  heat  of  the  magma. 

Heat  Carried  Away  by  Surface  Water. 

Any  attempt  to  estimate  the  amount  ot  heat  dissipated  by  a  hot-spring  valley 
of  the  character  arid  extent  of  the  Devil’s  Kitchen  must  be  of  the  crudest,  but  even 
so  such  an  attempted  estimate  can  not  fail  to  have  a  certain  amount  of  interest. 
The  area  included  within  this  basin  is  roughly  1,300  feet  long  by  500  feet  wide, 


154 


though  the  hot  springs  themselves  are  more  or  less  concentrated  in  about  half  of 
that  area.  As  may  be  seen  from  the  map  (p.  92),  the  valley  is  drained  by  a  single 
stream  (fig.  76),  which  follows  a  winding  pathway  through  it.  On  July  1,  1922,  a 
rough  estimate  showed  the  volume  of  inflowing  water  in  this  stream  to  be  about  30 
cubic  feet  per  second,  the  outflowing  water  at  the  east  end  to  be  about  36  cubic  feet 
per  second,  a  gain  of  perhaps  15  per  cent,  which  was  of  course  contributed  from  the 
various  springs,  both  hot  and  cold,  and  the  seepage  water  draining  in  from  the  steep 
sides  of  the  valley.  The  gain  in  temperature  from  inlet  to  outlet  was  about  6°. 
From  these  figures  one  may  roughly  calculate  the  total  heat  received  and  carried 
out  by  the  stream  alone  to  be  of  the  order  of  500,000,000  kg.  cals,  in  each  24  hours. 
To  this  a  considerable  quantity  must  be  added  for  the  loss  by  evaporation  over  the 
porous  surface  of  the  ground,  the  hot  springs,  and  the  main  stream. 

August  1 7,  1923,  represented  a  nearer  approach  to  mid-season  dryness  than  any 
other  visit  we  were  privileged  to  make  there.  The  total  intake  water  in  the  main 
stream  was  then  about  25  cubic  feet  per  second,  and  the  corresponding  quantity  at 
the  outflow  about  24  cubic  feet  per  second,  that  is,  in  the  main  drainage  channel  the 
inflow  and  outflow  from  the  Devil’s  Kitchen  was  substantially  equal,  indicating 
materially  smaller  accessions  of  surface  water  in  passing  through  the  hot-spring 
area  and  presumably  also  considerably  increased  evaporation.  Against  this  we 
may  set  the  fact  that  the  temperature  of  the  inflowing  water  was  n.8°,  while  the 
temperature  at  the  outlet  was  19. 20,  an  increase  of  7.40  during  the  period  of  flow 
through  the  basin.  Very  roughly  these  numbers  indicate  about  400,000,000  kg. 
cals,  of  heat  carried  away  by  the  stream  on  August  17,  1923,  compared  with 
500,000,000  on  July  1  of  the  previous  year.  Inasmuch  as  the  heat  actually  con¬ 
tributed  to  the  basin  from  below  is  presumably  substantially  constant  this  diminu¬ 
tion  in  the  heat  carried  away  by  the  stream  is  to  be  supplied  by  the  increase  in  the 
loss  by  evaporation.  This  would  seem  to  be  a  reasonable  analysis  of  the  conditions, 
but  the  undetermined  losses  by  radiation  and  evaporation  deprive  the  figures  of 
any  considerable  quantitative  significance.  In  spite  of  this  fact  the  figures  are 
interesting. 

SOURCE  OF  THE  WATER. 

Surface  Water. 

The  Lassen  springs  occur  in  small  natural  drainage  basins  in  a  country  where, 
judging  by  the  records  of  the  U.  S.  Weather  Bureau  for  neighboring  stations,  the 
mean  annual  precipitation  must  be  above  40  inches.1 

1  Estimated  from  data  contained  in  a  private  communication  from  Mr.  P.  C.  Day,  climatologist,  U.  S.  Weather  Bureau, 
which  were  as  follows: 


Elevation. 

Precipitation. 

feet 

ins . 

Canon  Dam . 

4,570 

42 

Greenville . 

3,600 

45.5 

Butte  Valiev . 

4,020 

49.5 

Chester . 

4,550 

36.0 

Westwood . 

4,000 

33.0 

Considering  the  higher  elevation  of  the  slopes  which  drain  into  the  hot-spring  areas,  the  above  estimate  is  conservative. 


155 


In  April  and  May  the  snow  lies  deep  on  the  mountain  slopes,  the  valleys  are 
watered  by  perennial  streams,  and  sometimes  cold  pools  occur  associated  with  the 
hot  ones.  In  all  the  areas  there  are  pools  much  cooler  than  the  hot  springs,  which 
are  best  accounted  for  by  the  presence  of  surface  water.  At  the  Geyser,  the  Boiling 
Lake,  the  Devil’s  Kitchen,  and  Bumpass  Hell  indubitable  cooling  effects  (Plate  7, 
No.  1)  can  at  times  be  traced  to  cold  streams  which,  when  swollen  by  the  melting 
snows,  encroach  directly  on  hot  springs  and  pools,  and  while  this  fact  does  not  prove 
that  meteoric  water  finds  its  way  into  the  springs  beneath  the  ground,  there  is 
obviously  a  considerable  supply  very  close  at  hand. 

SEASONAL  CHANGES  IN  THERMAL  ACTIVITY. 

In  our  earlier  visits  to  the  Lassen  Park  we  gained  the  impression  that  the  springs 
were  responsive  to  seasonal  changes,  but  the  recorded  evidence  left  much  to  be 
desired.  In  1922,  therefore,  more  systematic  observations  were  undertaken.  Since 
the  Boiling  Lake  and  the  Devil’s  Kitchen  were  the  most  conveniently  located  hot- 
spring  areas,  the  observations  were  practically  confined  to  them.  Work  was  begun 
at  the  Boiling  Lake  on  June  15,  when  the  higher  slopes  were  completely  covered 
with  snow.  At  that  time  the  lake  and  springs  were  full  of  water;  even  some  of  the 
mud  pots  contained  small  pools  of  water  in  their  craters,  while  others  were  partially 
or  wholly  submerged  by  the  lake.  By  July  9,  when  most  of  the  snow  had  melted, 
the  small  cold  stream  flowing  into  the  lake  had  dried  up  completely  and  the  dis¬ 
charge  from  it  had  almost  ceased.  Within  the  same  interval  the  water-level  of  the 
springs— most,  if  not  all  of  them — had  fallen  a  foot  or  more.  The  fall  was  parti¬ 
cularly  noticed  in  Nos.  1,  4,  8,  11,  and  the  springs  of  group  5.  A  small  hot  pool 
(8o°  C.)  close  to  the  cold  inlet  had  dried  up  completely.  During  these  weeks  there 
had  been  little  change  in  the  temperature  of  the  springs.  With  one  exception 
(No.  1)  their  pools  are  very  small  and  the  heat  was  apparently  sufficient  to  keep 
them  boiling,  even  at  high  water. 

In  August  1923,  only  the  larger  springs  contained  water,  the  smaller  ones  had 
shrunk  to  the  proportions  of  feeble  steam  fumaroles.  The  mud  pots  likewise 
showed  the  effects  of  a  greatly  reduced  water  supply;  they  had  become  considerably 
deeper  and  more  violently  active  (volcanic),  though  the  amount  of  the  participating 
material  (mud)  was  much  smaller  (fig.  77). 

At  the  Devil’s  Kitchen  similar  changes  were  noticed,  though  they  were  not  so 
carefully  followed.  However,  in  1922  the  volume  of  the  steam  in  the  fumaroles  of 
the  east  end  of  the  Kitchen  waned  decidedly  as  summer  advanced. 

In  the  mud  pots,  too,  obvious  changes  were  seen  with  the  advancing  season. 
At  the  Boiling  Lake  the  water  in  Nos.  6  and  7  dried  out  perceptibly,  the  temperature 
increased  a  little,  and  sputtering  became  more  active.  A  bit  of  former  evidence 
now  became  clear.  On  May  25,  1916,  the  mud  volcano,  No.  13,  Devil’s  Kitchen, 
was  sputtering  quietly.  On  June  8  it  was  in  active  eruption,  throwing  mud  in  all 
directions  to  the  height  of  10  or  12  feet,  while  the  muddy  ground  all  about  it  was 
obviously  drying  out  and  mud  cracks  appeared.  If  the  water  supply  falls  off  while 
the  heat  supply  keeps  up  the  effect  is  naturally  a  more  violent  boiling.  The  thick 
mud  offers  greater  resistance  to  the  passage  of  steam  and  other  gases  which,  in 


156 


overcoming  it,  produce  a  miniature  eruption.  At  that  time  we  had  no  opportunity 
to  follow  the  process  further,  but  a  continued  reduction  in  the  water  supply  should 
logically  produce  a  steam  jet  or  little  fumarole,  the  steam  of  which  may  not  be 
visible  under  ordinary  weather  conditions. 

These  later  stages  have  actually  been  observed  both  in  1922  and  1923  in  other 
localities  in  this  region.  Certain  small  mud  pots  at  the  Boiling  Lake  (west  of  No. 
6)  displayed  considerable  activity  early  in  our  visit  (1922),  but  declined  later  and 
finally  appeared  extinct. 

Hot  springs  pass  through  transition  stages  of  activity  similar  to  the  mud  pots, 
which  very  naturally  find  explanation  in  variations  in  the  supply  of  surface  water. 
Thus  at  times  some  springs  spout  to  a  much  greater  height  than  at  others,  (cf. 


Fig.  77. — June,  1923.  Large  mud  pot  at  Bumpass  Hell  (Fig.  50,  No.  1  7). 

Active  at  the  bottom.  Color,  battleship  gray.  Photo  Day. 

Plate  7).  Variations  of  this  character  have  been  noticed  at  the  Geyser,  at  the 
Devil’s  Kitchen  (No.  3),  and  at  Bumpass  Hell  (No.  14).  The  phenomenon  has  not 
been  studied  with  the  same  detail  as  the  activity  of  the  mud  pots,  hut  in  August 
1923,  when  the  ground  was  drier  than  it  had  been  at  the  time  of  our  previous 
visits,  a  larger  number  of  springs  were  spouting. 

VARIATION  IN  THERMAL  ACTIVITY  IN  DIFFERENT  YEARS. 

In  restricted  localities  within  the  hot-spring  areas  decided  differences  have 
been  observed  in  different  years.  Thus  in  1922,  and  particularly  in  1923,  one  of 
the  most  active  spots  at  the  Boiling  Lake  (fig.  59,  No.  8),  was  on  the  promontory 
at  the  foot  of  the  slide  on  the  northeast  end.  Within  an  area  of  perhaps  10  yards 
square  were  more  than  a  dozen  springs  in  which  muddy  water  was  boiling  violently 
to  the  height  of  several  inches.  Neither  in  1915  nor  in  1916  had  any  springs  been 
observed  here.  At  the  Devil’s  Kitchen  there  was  a  similar  and  much  larger  area  in 
the  northwest  corner.  The  activity  must  have  been  very  slight  there  in  1916,  for 


. 


ttik 


lMAHt 


PLATE  13 


July  10,  1915.  Deep  hot  pool  at  Bumpass  Hell  (No.  16,  Fig.  50)  nearly  filled  with  water.  Color 
bright  bird’s-egg  blue.  Fumarole  vigorous  and  noisy.  Photo  Day. 


July,  1922.  Same  pool  empty.  Great  fumarole  extinct. 


Photo  Day. 


157 


it  passed  unnoticed,  while  in  1922  there  were  a  large  number  of  boiling  springs  and 
mud  pots,  some  of  them  violent.  On  the  same  (north)  side  of  Warner  Creek  and  east 
of  No.  10  many  mud  pots,  which  in  1916  were  seemingly  extinct,  showed  consider¬ 
able  activity  in  1922  and  1923.  Bumpass  Hell  offers  an  interesting  case  (Plate.  13). 

We  attribute  the  differences  to  a  greater  supply  of  surface  water  in  1922  and 
1923  during  the  time  of  our  observations.  Differences  of  this  sort  may  possibly  be 
caused  by  variations  in  the  total  annual  precipitation,  but  the  differences  under 
discussion  are  apparently  conditioned  by  the  rate  of  melting  and  the  eventual  dis¬ 
appearance  of  the  snow.  Comparison  of  the  weather  records  indicates  that  more 
snow  fell  in  the  winter  of  1916  than  in  1922,  but  in  the  latter  year  the  snow  lingered 
late.  In  consequence  of  this  our  arrival  in  the  Park  was  postponed  a  full  month 
beyond  the  time  when  we  began  work  in  1916.  The  amount  of  snow  still  unmelted 
and  the  tardy  appearance  of  the  spring  flowers  evinced  the  lateness  of  the  season. 
The  large  volume  of  water  at  the  Boiling  Lake  at  that  time  has  already  been  men¬ 
tioned  (p.  155).  At  the  Devil’s  Kitchen  Warner  Creek  was  brim  full,  many  small 
rills  were  pouring  over  the  high  southern  wall  of  the  basin,  some  of  the  springs  were 
obviously  affected  by  inflowing  surface  water,  and  the  flats  near  the  brook  level 
between  the  points  marked  3  and  10  on  the  map  were  quite  muddy  and  the  footing 
less  secure  than  usual. 

SALT  PATCHES  AS  AN  INDICATION  OF  THE  STATE  OF  THE  GROUND. 

In  May  and  June,  1916,  salt  patches  were  found  in  all  the  hot-spring  areas. 
Some  of  them  appeared  and  visibly  increased  as  the  ground  dried  out.  The  same 
course  of  development  was  observed  in  one  place  in  the  Devil’s  Kitchen  in  1922,  but 
in  that  year  hardly  any  patches  were  seen,  and  these  were  of  the  scantiest  character. 
From  these  facts  the  inference  was  drawn  that  the  appearance  of  the  salts  depended 
on  the  moisture  in  the  ground,  and  that  as  a  corollary  the  latter  season  was  wetter 
than  the  former.  But  in  August  1923,  when  other  convincing  facts  led  to  the  con¬ 
clusion  that  the  ground  was  drier  than  it  was  on  either  of  our  former  visits,  no  salts 
at  all  were  observed.  A  further  consideration  ot  the  matter  makes  it  quite  improbable 
that  the  salts  remain  indefinitely  in  the  ground  of  any  particular  area,  merely 
moving  up  and  down  in  response  to  variations  of  the  weather.  In  very  dry  times 
there  is  too  little  moisture  to  move  them  at  all,  while  in  wet  seasons  they  are  prob- 
bably  washed  down  into  some  near-by  hot  spring  or  into  some  outlet  stream.  The 
formation  of  more  salt  and  its  subsequent  deposition  at  the  surface  will  depend  on 
the  amount  of  volcanic  gas  that  permeates  the  area  in  any  particular  time  (p.  141) 
and  on  a  proper  distribution  of  ground  water  to  maintain  just  the  right  degree  of 
moisture,  for  neither  the  flow  ot  gas  nor  the  flow  of  water  through  the  same  section 
of  ground  can  be  at  all  constant.  Both  are  bound  to  change  in  a  region  where  dis¬ 
integration  and  slumping  are  in  active  progress  and  where  the  difference  in  the 
water  supply  from  early  spring  to  midsummer  is  so  great.  The  presence  or  absence 
of  salts  can  not,  therefore,  of  itself  be  regarded  as  an  index  of  the  amount  of  moisture 
in  the  ground,  but  the  evidence  which  precedes  this  discussion  is  still  valid  and 
indicates  that  in  June  and  early  July  1922  the  ground  was  wetter  than  at  the  time 
of  our  former  visit,  while  in  August  1923  it  was  drier. 


158 


RECENT  OUTBREAK  OF  THERMAL  ACTIVITY. 

Some  time  between  1916  and  1922  a  new  outbreak  of  thermal  activity  occurred 
in  the  east  end  of  the  Devil’s  Kitchen  (figs.  78,  79).  At  the  earlier  date  the  activity 
in  this  locality  was  chiefly  on  the  left  bank  of  Warner  Creek.  On  the  right  bank 


Fig.  78.  June,  1922.  Fresh  outbreak  of  thermal  activity  in  the  Devil’s 
Kitchen.  Photo  Day. 


Fig.  79.  —  The  same  region  in  July,  1923.  All  of  the  central  portion  of 
the  picture  has  settled  8  to  I  0  feet.  Photo  Day. 

there  was  a  small  hot  stream  (fig.  8o) — a  mere  rill  formed  by  the  discharge  of  several 
insignificant  hot  springs  flowing  down  from  No.  15  and  emptying  into  the  creek,  and 
a  single  fumarole.  In  1922  the  stream  had  disappeared  and  its  place  was  occupied 
by  a  deep  furrow,  from  the  bottom  of  which  several  large  active  fumaroles  (fig.  78), 
occurring  at  intervals,  poured  out  a  considerable  cloud  of  steam.  The  temperature 


159 


in  all  the  fumaroles  was  practically  that  of  boiling  water  at  this  spot,  namely,  940. 
About  25  feet  to  the  southeast,  close  up  to  the  steep,  high  bank  bounding  the  Kit¬ 
chen  in  that  direction,  there  now  appeared  a  deep  trench  approximately  parallel  to 
the  bank,  from  which  issued  the  most  active  hot  springs  in  the  whole  region.  Both 
furrows  and  trenches  were  obviously  formed  by  intersecting  slump  holes  which  were 
especially  well  marked.  Each  hole  in  this  trench  was  partially  filled  by  a  hot 
muddy  pool  emptying  into  the  next  below.  Into  the  uppermost  pool  throughout 
the  time  of  our  stay  in  1922  a  rill  of  cold  water  was  flowing,  yet  the  temperature  of 
the  pools  close  to  the  springs  never  varied  more  than  a  degree  or  two  from  the  boil- 


Fig.  80. — May  20,  1916.  Wonderful  magenta  terraces  colored  by  oxide  of  iron.  Obliter¬ 
ated  by  the  new  outbreak  at  the  Devil’s  Kitchen  (1923).  Photo  Day. 


ing-point.  The  surface  of  the  lowest  pool  was  constantly  stirred  by  pulsating  jets 
of  hot  water.  In  No.  24  appeared  a  dome-shaped  fountain  of  considerable  volume 
(probably  2  feet  high  and  2  feet  across),  spasmodically  leaping,  splashing,  and 
roaring.  The  uppermost  spring  (No.  23)  was  the  most  spectacular  (fig.  81).  It 
took  the  form  of  a  noisy  jet  of  steam  and  hot  water  shot  out  of  a  large  nozzle,  from 
which  it  emerged  at  an  angle  with  a  pulsating  motion,  dissipating  itself  in  a  cloud 
of  steam  at  a  distance  of  5  or  10  feet.  The  subsidence  which  formed  the  seat  of 
this  new  activity  was  evidenced  by  the  form  of  the  depressions  and  by  the  uprooting 
of  good-sized  trees  (figs.  78,  79). 


160 


During  the  same  period  (1916-1922)  a  decided  decline  occurred  on  the  opposite 
bank  of  the  creek,  where  in  1916  there  had  been  a  line  of  small,  vigorous  hot  springs 
and  a  good-sized  and  quite  active  fumarole  (fig.  47,  No.  20).  The  ground  along 
the  north  bank  of  the  creek  at  that  time  was  riddled  by  chemical  action  and  afforded 
a  very  uncertain  footing  (fig.  75).  In  1922  all  had  changed  materially.  Spring 
No.  19  could  no  longer  be  located.  A  shallow  depression  containing  boiling  water 

was  found  where  No.  20  had  been.  No. 
21  apparently  still  existed,  but  was  much 
less  active  than  formerly.  The  bank 
was  generally  firmer  and  drier  and  some 
incrusting  salts  were  observed.  In  Au¬ 
gust  1923,  No.  23  was  still  active  as  a 
roaring  jet  of  steam  but  carrying  little 
water,  while  No.  24  had  become  reduced 
to  a  shallow,  turbid  pool  showing  but  a 
fraction  of  the  activity  of  the  year  be¬ 
fore.  Both  the  steam  jet  and  the  springs 
showed  the  temperature  of  boiling  water, 
while  the  ground  about  the  springs  was 
unpleasantly  hot  and  dry.  The  under¬ 
mining  of  trees  and  slumping  of  the 
ground  had  progressed  farther  into  the 
south  bank,  probably  during  the  previous 
spring,  for  the  cold  inlet  stream  was  now 
dry.  Both  these  pools  and  others  to  the 
north  were  now  considerably  deeper  than 
in  1922. 

Changes  of  a  character  similar  to 
these  have  been  observed  elsewhere. 
Hague1  says  of  the  Yellowstone  Park: 
“New  springs  are  continually  reaching 
the  surface  and  old  ones  are  becoming 
extinct.”  Within  a  short  time  one  of  the 
largest  geysers  in  the  Park  has  broken  out. 

A  comparison  of  these  changes  to  the 
rejuvenation  and  decline  of  activity  in 
volcanic  craters,  where  great  fluctuations 
in  temperature  are  known  to  take  place, 
is  naturally  suggested.  While  of  course  the  temperature  of  spring  waters  is  limited 
by  the  boiling-point,  the  acquisition  of  a  new  store  of  energy  by  the  batholith  from 
which  the  heat  of  the  springs  is  derived  is  a  possibility.2  However,  a  more  plausible 


~ 


Fig.  81. — June,  1922.  Spouting  spring 
in  Devil’s  Kitchen  (No.  23,  Fig.  47). 
A  jet  of  hot  water  and  steam  8  or 
10  ft.  in  height.  Photo  Day. 


1  Bull.  Geol.  Soc.  Amer.  22,  1 14,  1911. 

2  Thus  the  temperature  of  the  famous  Solfatara  of  Pozzuoli  near  Naples  rose  about  70°  C.  in  a  period  of  about  50  years 
(1856-1905).  See  Wolff,  Vulkanismus,  vol.  I,  p.  600,  1914. 


161 


explanation  of  the  phenomena  described  is  found  in  the  changes  which  may  occur 
along  the  paths  by  which  hot  water  and  steam  reach  the  surface.  The  ground  of 
these  areas  is  gradually  disintegrating  under  the  influence  of  thermal  action  into 
products  which  are  slowly  carried  away  by  flowing  water;  the  ground  is  undermined 
and  the  surface  portions  slump  in.  These  are  observed  facts.  That  steam  should 
slowly  cut  for  itself  new  passages  to  the  surface,  that  slumping  should  dam  up  old 
channels  and  divert  the  water  to  new  paths  or  should  open  up  new  apertures,  seems 
not  improbable. 

The  data  are  probably  insufficient  for  a  detailed  explanation  of  the  changes  in 
the  Devil’s  Kitchen,  but  what  we  have  are  suggestive.  The  new  outbreak  and  the 
decline  of  earlier  activity  may  be  intimately  connected,  for  both  spring  groups 
probably  derive  their  water  supply  from  the  same  collecting  ground — the  long  steep 
slope  to  the  south.  Springs  19  to  21  lie  near  the  creek  level  and  the  new  springs  are 
on  the  slope  above  mentioned  at  a  higher  elevation.  There  are  one  or  two  hot 
springs  rising  in  the  bed  of  the  creek  between  the  two  groups.  The  decline  appears 
to  be  certainly  due  to  a  local  interruption  of  the  water  supply  of  springs  19  to  21, 
for  ground  temperatures  in  that  vicinity  are  still  high,  reaching  a  maximum  of  940, 
at  depths  of  1  to  3  feet.  If  the  two  groups  of  springs  derive  their  supply  from  the 
same  source,  the  slumping  in  of  the  ground  at  the  higher  elevation  may  bring  most 
of  the  water  to  the  surface  and  thus  impoverish  the  other  group. 

In  the  two  preceding  sections  we  have  endeavored  to  account  for  variations  in 
the  volume  of  water  observed  in  different  years  in  the  two  localities  which  have  been 
most  closely  studied.  Two  factors  appear  to  be  responsible  for  these  variations — 
a  change  in  the  total  volume  of  water  and  a  change  in  its  distribution  ;  but  to  decide 
in  each  case  which  is  the  cause  of  the  observed  variation  would  probably  necessitate 
a  close  and  continuous  observation  of  the  phenomena  such  as  we  have  not  been  able 
to  give. 

FLUCTUATIONS  IN  THE  COMPOSITION  OF  THE  WATERS. 

G.  A.  Waring  in  his  “  Springs  of  California”  1  gives  a  brief  description  of  the  hot- 
spring  areas  in  the  Lassen  Park.  He  publishes  two  analyses  of  the  waters  made  by 
F.  M.  Eaton  of  Oakland,  California,  which,  so  far  as  we  know,  are  the  only  ones 
ever  made  of  the  waters  of  this  region  excepting  our  own.  The  analyses  are  worth 
quoting  (see  table  11).  The  first  water  sample  is  “from  a  large  pool  in  the  centre 
of  the  area”  (Devil’s  Kitchen).  This  description  agrees  well  with  pool  No.  5 
(see  fig.  47),  an  analysis  of  the  water  of  which  is  given  in  the  table  for  comparison. 
The  discrepancy  in  composition  between  the  two  is  very  striking;  the  soluble  salts 
are  1.12  gram  (Eaton’s  result)  and  0.79  gram  (our  result),  respectively.  It  is 
possible  that  Eaton  may  have  referred  to  pool  9  instead  of  pool  5,  the  water  from 
which  was  not  analyzed  by  us,  but  it  is  noteworthy  that  none  of  the  waters  in  the 
Devil’s  Kitchen  which  we  did  analyze  were  so  concentrated  in  soluble  salts  as  the 
waters  of  pool  5. 

Eaton’s  second  sample  was  from  Bumpass  Hell  Springs.  This  may  seem  to 
the  reader  entirely  indefinite,  considering  the  size  of  the  area,  but  anyone  who  has 


1  U.  S.  Geol.  Survey,  Water  Supply  Paper  338,  pp.  140-143,  1915. 


162 


visited  it  will  recognize  that  there  is  one  pool,  No.  14  (Plate  12),  now  divided  into 
two,  which,  on  account  of  its  size  and  its  activity,  is  more  impressive  than  any  other. 
The  comparison  of  Eaton’s  analysis  with  our  analysis  of  the  water  from  No.  14 
shows  that  the  soluble  salts  are  0.24  gram  (Eaton’s  result)  and  0.81  gram  (our 
result),  respectively.  There  is  only  one  other  pool  which  it  is  at  all  likely  anyone 
would  select  as  representative  of  Bumpass  Hell,  namely,  No.  4  (figs.  50,  52),  but 
here  also  the  difference,  though  smaller,  is  quite  beyond  the  limits  of  analytical  error. 


Table  ii. — Comparison  of  Analyses  of  Spring  Waters  in  Devil’s  Kitchen  and 

Bumpass  Hell. 

[Samples  taken  several  years  apart.] 


Locality. 

H. 

NH<. 

K. 

Na. 

Ca. 

Mg. 

Al. 

Fe". 

Fe"'. 

so4. 

Cl. 

SiCL. 

BA. 

Devil’s  Kitchen  Springs, 
hot  pool  near  the 
center  of  the  area. 
(Analysis  1909-10  hy 

* 

F.  M.  Eaton) . 

10 

9.7 

41 

20 

11 

50 

11 

963 

trace 

286 

Pool  5  (fig.  47)  Devil’s 

Kitchen.  (Analysis 

1916,  the  authors) . . . 
Bumpass  Hot  Springs. 

7 

2.6 

9 

43 

38 

14 

10 

30 

none 

617 

trace 

167 

(Analysis  1909-10  by 

0.37 

14 

16 

8.9 

5.1 

53 

1 

4 

141 

trace 

124 

F.  M.  Eaton) . 

Spring  14  (fig.  50)  Bum- 

pass  Hell.  (Analysis 
1916,  the  authors) .... 

7 

15 

13 

29 

7 

4.5 

28 

17.5 

5 

681 

2 

236 

4 

Spring  4  (fig.  50)  Bum- 

pass  Hell.  (Analysis 
1916,  the  authors). .  . . 

none 

128 

4 

33 

7 

2 

none 

4 

4 

419 

trace 

138 

84 

This  evidence  admittedly  leaves  much  to  be  desired,  hut  interpreted  according 
to  our  best  judgment  it  indicates  fluctuations  in  composition  which  are  in  accord 
with  all  the  rest  of  the  evidence  in  supporting  a  variable  rather  than  a  constant 
flow  of  water  from  the  springs. 

Altogether,  the  evidence  lor  the  surface  origin  of  water  in  the  Lassen  springs  is 
so  convincing  to  an  observer  that  if  the  hypothesis  of  juvenile  or  magmatic  water 
had  never  been  proposed  the  entire  adequacy  of  the  simpler  theory  to  account  for 
all  the  water  would  probably  never  have  been  questioned. 

The  Presence  of  Magmatic  Water. 

Nevertheless  there  are  reasons  for  concluding  that  a  portion  of  the  water  in 
these  springs  is  magmatic — reasons  so  cogent  that  the  conclusion  appears  almost 
inescapable.  We  have  already  found  in  the  presence  of  the  volcanic  gases  in  the 
springs  evidence  of  a  hot  magma  from  which  the  heat  arises.  We  have  concluded 
that  a  hot  magma  must  of  necessity  give  off  volcanic  gases  as  well  as  heat,  because 
all  igneous  rocks,  which  once  were  magmas  themselves,  give  off  similar  gases  when 
heated.  Furthermore ,  heated  igneous  rocks  almost  invariably  give  off  more  steam  than 
all  other  gases  put  together. 

Hot  magmas  in  all  probability  always  give  off  magmatic  water,  and  any  hot 
spring  which  gives  off  volcanic  gases  should  also  contain  some  magmatic  water. 


163 


A  possible  step  in  the  direction  of  estimating  the  amount  of  it  would  be  to  determine 
the  ratio  of  the  gases  to  the  total  water  in  the  springs,  and  then  to  compare  this 
ratio  with  that  of  the  gas  to  the  steam  in  fumaroles  and  the  ratio  of  gas  to  water  in 
rocks.  An  intimation  of  the  order  of  magnitude  of  the  magmatic  water  might  he 
arrived  at  in  this  way. 

RELATION  OF  HOT  SPRINGS  TO  THE  MAGMA. 

Views  of  Other  Investigators. 

As  regards  their  view  of  hot  springs,  geologists  divide  into  two  schools.  One 
school  has  held  the  perfectly  definite  conception  that  hot  springs  are  produced  hy 
meteoric  water  circulating  under  the  influence  of  gravity  through  hot  ground. 
Many  of  this  school  would  probably  admit  that  some  of  the  volatile  products  as 
well  as  the  heat  were  derived  from  a  deep-seated  source.  The  other  school,  ap¬ 
proaching  the  subject  from  a  study  of  the  mineral  veins  and  their  relation  to  the 
igneous  rocks,  has  held  that  the  water,  or  some  of  it,  was  juvenile,  though  their 
ideas  of  how  this  water  is  conveyed  to  the  surface  do  not  appear  to  have  been  clearly 
worked  out. 

Plague  1  concluded  that  the  hot  waters  of  the  Yellowstone  springs  were  of 
surface  origin,  and  Bunsen  2  reached  the  same  conclusion  regarding  the  hot  springs 
of  Iceland,  though  the  latter  qualified  his  statement  by  the  admission  that  some  of 
the  water  there  was  derived  from  the  heated  rocks.  This  is  doubtless  true  of  a 
zone  which  lies  between  the  batholith  and  the  zone  of  ground  water.  In  the  latter 
the  decomposition  products,  kaolin,  alunite,  and  silica,  would  contain  more  water 
than  the  mass  of  most  igneous  rocks  from  which  they  were  derived.  In  that  case 
water  would  be  withdrawn  from  the  general  supply. 

Thorkelsson  3  is  less  specific  in  his  statements  than  Hague  or  Bunsen.  He 
concludes  that  the  alkaline  springs  of  Iceland  contain  at  any  rate  considerable  at¬ 
mospheric  water,  but  avoids  further  speculation. 

More  recently  Schneider  4  has  published  an  important  contribution  to  this 
subject.  His  observations  prove  in  a  convincing  manner  the  close  relation  of 
ground  water  to  the  Icelandic  hot  springs.  At  Krisuvik,  for  instance,  where  hot 
springs,  mud  pots,  and  solfataras  occur  together,  the  spouting  springs  are  rendered 
more  active  by  stopping  up  the  solfataras.  If  the  springs  are  stopped  up  by  turf, 
the  mud  volcanoes  respond  by  greater  activity,  while  if  the  surface  waters  above  the 
solfataric  field  are  dammed  up,  steam  replaces  the  water  jets  and  the  mud  volcanoes 
cease  their  activity.  At  Cape  Reykjanes,  Schneider  states  that  the  geysers  are 
strongly  affected  by  the  ebb  and  flow  of  the  tide.  Schneider  believes  that  all  the 
water  of  hot  springs  is  atmospheric  and  that  they  contain  nothing  juvenile  except 
the  volcanic  gases,  which,  as  a  follower  of  Brun,  he  regards  as  anhydrous. 

Respecting  the  hot  springs  of  New  Zealand,  it  is  the  view  of  Park  5  that  both 
alkaline  and  acid  waters  have  a  common  origin,  and  this  is  quite  probably  mag- 

1  Hague,  Bull.  Geol.  Soc.  Amer.  22,  121,  1911. 

2  Bunsen,  Liebig’s  A  nnalen,  62,  especially  1-5,  1847. 

3  Thorkelsson,  Memoires  de  V Academie  royale  des  Sciences  et  Lettres  de  Danemark ,  8,  especially  p.  260,  1910. 

4  Schneider,  Geolog.  Rundschau ,  4,  65,  1913. 

6  Park,  Geology  of  New  Zealand,  pp.  178,  etc. 


164 


matic.  On  the  other  hand,  there  are  well-known  facts  difficult  to  explain  on  that 
hypothesis,  notably  the  phenomena  of  the  great  geyser  of  Waimangu  and  its  relation 
to  Tarawera  Lake.1 

The  Magmatic  Water 

Some  new  light  on  the  subject,  we  believe,  is  to  be  gained  by  considering  hot 
springs  as  one  of  the  phases  of  volcanism  and  closely  related  to  the  fumaroles. 
Hot  springs  and  fumaroles  often,  if  not  generally,  occur  together.  There  are  fuma¬ 
roles  in  some  of  the  hot-spring  areas  under  discussion,  notably  at  Bumpass  Hell 
and  the  Devil’s  Kitchen.  Whether  the  one  or  the  other  occurs  is  no  doubt  a  ques¬ 
tion  of  the  relation  of  heat  supply  to  water  supply.2  Any  magmatic  water  which  a 
fumarole  may  possess  must  find  its  way  to  the  surface  as  steam.  That  fumaroles 
actually  do  contain  magmatic  water  follows  from  the  behavior  of  an  igneous  rock 
when  heated.  Occasionally  also  field  evidence  may  indicate  that  the  water  of  a 
fumarole  is  entirely  magmatic.  This  is  true  of  the  well-known  fumarole3  at  the 
foot  of  the  cone  of  Etna.  As  the  temperature  of  a  fumarole  falls  the  exhalation  of 
steam  continues.  Not  until  it  reaches  the  critical  temperature,  strongly  modified  as 
it  is  by  the  soluble  matter  in  the  magma,  would  it  be  possible  for  the  water  to  con¬ 
dense,  and  not  then  unless  the  pressure  were  sufficiently  great.  The  experimental 
studies  of  G.  W.  Morey  4  indicate,  however,  that  the  vapor  pressure  of  water  in  the 
magma  would  be  so  reduced  by  the  soluble  matter  that  a  pressure  sufficient  to 
condense  the  water  would  only  serve  to  drive  it  back  into  the  magma.  In  other 
words,  if  water  is  to  leave  the  magma  at  all,  it  must  do  so  as  steam.  If  one  is 
inclined  to  argue  that  some  important  factor  has  been  omitted  from  the  discussion, 
invalidating  this  conclusion,  he  finds  himself  confronted  by  the  necessity  of  explain¬ 
ing  how  liquid  water  is  raised  to  the  suiface.  A  force  adequate  to  do  this  has  so  far 
not  been  suggested.  Of  course,  the  hydrostatic  pressure  of  a  column  of  colder 
water  from  the  surface  would  be  equal  to  this  work,  but  probably  few  if  any  geo¬ 
logists  believe  that  unbroken  columns  of  water  penetrate  down  far  enough  to  reach 
a  batholith.  As  to  the  means  by  which  magmatic  water  reaches  the  surface, 
another  line  of  reasoning  has  led  us  previously  to  the  same  conclusion. 

Acid  and  Alkaline  Springs. 

Fumaroles  commonly  contain  some  acid5  gases,  H2S,  S02,  HC1,  HF,  as  well  as 
C02,  while  hot  springs  may  be  either  acid  or  alkaline.  The  presence  of  these  gases 
is  satisfactorily  explained  as  the  result  of  a  hydrolysis  of  sulphide  and  halide  mole¬ 
cules  in  the  complex  magma  or  batholith  by  the  agency  of  steam.  The  volatile 
acid  products  of  the  reaction  are  continuously  cairied  off  in  the  gaseous  phase  of 

1  MacLaren,  Geol.  Mag.  3,  511,  1906. 

2  Wolff  says  ( Vulkanismus ,  p.  627)  that  a  decline  in  temperature  changes  fumaroles  into  hot  springs  This  is  not  a 
necessary  consequence.  In  the  Katmai  region,  Alaska,  many  extinct  fumaroles  have  resulted  from  this  cause.  The  forma¬ 
tion  of  a  hot  spring  is  of  course  also  dependent  on  topography  and  ground  structure  which  determine  at  what  points  water 
shall  come  to  the  surface. 

3 'this  fumarole,  the  Fummarola  o  Vuccaloru,  gives  ofF  an  enormous  volume  of  steam  after  9  months  of  rainless  weather 
(observation  of  1914).  Its  location  (less  than  1,000  feet  below  the  summit)  and  the  structure  of  the  mountain  also  lead  to  the 
view  that  its  water  can  not  be  meteoric. 

4  Journ.  Wash.  Acad.  Sci.  12,  219-230,  1922. 

6  Occasionally  also  fumarole  gases  are  alkaline  from  the  presence  of  ammonia  or  ammonium  carbonate. 


165 


the  system  and  may  thus  continue  to  be  given  off  for  long  periods.  If,  however,  it 
were  possible  for  a  magma  or  batholith  to  give  off  liquid  water,  the  solution  should 
always  be  alkaline,  for  we  know  that  the  principal  reaction  of  an  igneous  rock  with 
water  at  ioo°  is  the  hydrolysis  ot  the  silicates,  a  reaction  which  should  move  nearer 
to  completion  at  the  higher  temperature  of  the  batholith.  This  reaction  is  ob¬ 
viously  favored  by  the  solubility  of  the  alkali  hydioxides,  though  it  would  doubtless 
be  unimportant  if  the  water  were  given  off  by  the  batholith  in  the  form  of  steam  on 
account  of  the  slight  volatility  of  the  hydroxides.  Acid  elements,  like  the  halogens, 
sulphur  and  carbon  would  be  carried  off  by  liquid  as  well  as  by  gaseous  water,  but 
in  the  water  solution  they  would  take  the  form  of  salts — halides,  sulphides  and  car¬ 
bonates  or  bicarbonates.  The  halides  are  neutral,  the  sulphides,  carbonates,  and 
bicarbonates  are  alkaline.  We  have  reason  to  believe  that  a  magma,  and  in  a 
lesser  degree  a  batholith,  contains  more  sulphur,  and  in  some  instances  more 
halogens,  than  an  ordinary  igneous  rock,  but  that  these  elements  should  ever  reach 
such  a  proportion  as  to  be  capable  of  neutralizing  completely  all  the  alkali  from  the 
hydrolysis  of  the  silicates,  much  less  that  they  should  by  any  conceivable  reaction 
give  rise  to  free  acid,  is  quite  beyond  the  bounds  of  probability. 

On  the  other  hand,  acid  springs  are  the  logical  successors  of  acid  fumaroles,  if 
we  suppose  them  to  be  formed  by  ground  water  which  serves  to  condense  the  vol¬ 
canic  steam  and  acid  gases  arising  from  a  batholith.  Springs  which  contain  free 
hydrochloric  acid,  like  some  in  the  Yellowstone  Paik,  or  possibly  hydrofluoric  acid 
in  certain  instances,  are  thus  accounted  for,  while  springs  which  contain  free  sul¬ 
phuric  acid  can  only  be  explained  by  supposing  that  an  oxidation  of  the  original 
sulphur  gases  (H2S,  S,  S02)  occurs  after  they  come  into  contact  with  air  in  the  zone 
of  ground  water.  This  phase  of  the  problem  has  already  been  discussed.  Waters 
of  such  an  origin  may  emerge  from  the  ground  still  acid,  or  their  character  may  be 
changed  as  a  consequence  of  their  subsequent  history. 

Whatever  the  origin  of  the  acid,  it  will  attack  the  rock  as  soon  as  it  comes  in 
contact  with  it,  decomposing  it  in  a  manner  already  explained  (p.  140),  and  the  de¬ 
composition  will  proceed  as  long  as  the  contact  continues  or  until  the  acid  is  ex¬ 
hausted,  for  no  igneous  rock  can  remain  in  equilibrium  with  an  acid  spring-water. 
The  bases  in  the  rock  gradually  neutralize  the  acid  and  eventually,  unless  the  rock 
is  entirely  free  from  alkalies,  the  hydrolysis  of  the  alkali  silicates  will  produce  an 
alkaline  water.  Bunsen  1  convinced  himself  of  this  years  ago,  when  he  heated  an 
acid  spring-water  of  Iceland  with  the  powdered  rock  of  the  region.  When  the  two 
were  heated  for  some  hours  in  a  sealed  tube  at  about  ioo°  C.  the  solution  became 
alkaline  in  consequence  of  the  formatiop  of  sodium  and  potassium  hydroxides. 
Incidentally  the  iron  was  of  course  precipitated.  In  a  natural  spring-water  the 
caustic  alkalies  would  always  be  transformed  into  carbonates  or  bicarbonates  and 
the  alumina  as  well  as  the  iron  would  be  precipitated. 

From  a  chemical  point  of  view,  then,  an  acid  spring-water,  the  rock  it  traverses, 
and  the  decomposition  products  of  the  rock  constitute  a  system  in  process  of  change, 
and  the  composition  of  the  water  where  it  emerges  from  the  ground  will  depend  on 
a  number  of  conditions. 


1  Liebig  s  Annalen,  62,  52,  1847. 


166 


Still  holding  the  chemical  viewpoint,  we  see  that  the  problem  involves  the 
speed  of  the  reactions,  and  that  these  depend  on  the  physical  and  chemical  nature 
of  the  rock,  the  temperature,  and  the  time  of  contact  between  rock  and  acid.  It 
the  rock  is  rich  in  volcanic  glass,  like  that  in  the  Lassen  Park,  or  in  feldspathic 
minerals,  the  acid  will  be  neutralized  much  faster  than  by  a  rock  composed  chiefly 
of  pyroxenes  and  amphiboles.  Where  the  rock  is  cracked  and  seamed  its  active 
surface  is  obviously  increased,  and  the  speed  of  reaction  thus  promoted,  while  the 
influence  of  variations  in  temperature  is  obvious.  The  time  of  contact  between 
rock  and  acid  depends  not  only  upon  the  length  of  the  path  which  the  spring-water 
traverses  in  its  journey  beneath  the  ground,  but  also  upon  its  rate  of  percolation, 
which  in  turn  varies  with  the  topography  and  rock  structure. 

In  other  respects  the  acid  hot  spring  is  not  comparable  with  the  chemical 
systems  ordinarily  studied  in  laboratories;  the  waters  move  from  point  to  point, 
laving  successive  portions  of  rock,  and  finally  leave  the  field  before  equilibrium  can 
be  established.  Moreover,  the  supply  of  acid  is  continually  renewed  and,  according 
to  our  hypothesis,  continually,  though  probably  not  regularly,  reduced  in  concentra¬ 
tion  as  the  waters  percolate.  If  the  acid  supplied  to  a  particular  spring  is  relatively 
small  in  quantity,  and  this  will  depend  in  the  present  case  not  only  on  the  concentra¬ 
tion  of  hydrogen  sulphide  in  the  volcanic  gases,  but  on  the  conditions  which  favor 
its  oxidation  and  on  the  proportion  of  surface  water  diluting  the  gases,  so  much  the 
greater  will  be  the  chance  that  the  water  of  the  spring  as  it  issues  from  the  ground 
will  be  alkaline.  Local  differences  in  the  volcanic  emanation,  like  local  differences 
in  the  composition  of  a  rock,  may  occur  in  the  same  field,  or  changes  in  the  composi¬ 
tion  of  the  original  gases  may  arise  from  reactions  with  the  rock  as  the  gases  move 
through  a  zone  of  diminishing  temperature  toward  the  surface. 

For  the  sake  of  simplicity  we  have  considered  the  formation  of  the  acid  and 
the  attack  of  the  acid  on  the  rock  as  separate  processes,  but  it  is  practically  certain 
that  the  two  go  on  together.  If  this  is  the  case,  the  rate  of  the  former  reaction 
must  be  the  greater. 

Variations  of  the  above  character  in  conditions  beneath  the  ground  may  thus 
result  in  both  acid  and  alkaline  springs  in  the  same  area. 

COEXISTENCE  OE  ACID  AND  ALKALINE  SPRINGS. 

Acid  and  alkaline  springs  occur  together  in  the  Lassen  district,  but  the  number 
of  the  latter  must  be  small,  as  only  four  have  been  found,  all  but  one  in  the  Devil’s 
Kitchen,  and  these  are  only  slightly  alkaline.  These  four  are  lowest  in  S04  of  any 
springs  in  the  region,  only  one  slightly  acid  spring  containing  so  small  a  quantity. 
From  this  we  may  infer  that  the  cause  of  the  alkalinity,  or  rather  the  principal  condi¬ 
tion  favoring  it,  is  a  local  limitation  of  the  acid  supply.  The  outstanding  fact  is  that 
the  waters  are  especially  dilute  in  this  strong  acid  radical.  The  cause  of  this  is 
attributed  to  the  presence  of  a  larger  quantity  of  surface  water  to  a  given  amount 
of  volcanic  gas,  rather  than  to  any  considerable  variation  in  the  composition  of 
the  latter. 


167 


None  of  these  springs  so  far  as  observed  is  depositing  any  siliceous  sinter,  as 
geysers  invariably  do.1  The  reason  for  this  is  unknown,  and  we  shall  not  hazard  a 
guess  until  the  subject  has  been  more  thoroughly  studied. 

Acid  and  alkaline  springs  occur  together  in  all  the  great  hot-spring  regions  of 
the  globe.  Bunsen2  says  that  in  Iceland  the  alkaline  springs  are  the  most  widely 
distributed  and  form  the  majority  of  the  warm  and  hot  springs  of  the  island.  Hague3 
says  of  Yellowstone  Park:  “The  volume  of  the  siliceous  alkaline  waters  far  exceeds 
that  of  the  acid  type.  On  the  other  hand  the  latter  occur  more  widely  distributed.” 
According  to  Park:4  “The  waters  which  rise  to  the  surface  in  the  region  about 
Lake  Rotorua  are  alkaline,  acid,  or  neutral.” 

TIME  RELATION  BETWEEN  THE  ACID  AND  ALKALINE  SPRINGS. 

If  our  hypothesis  of  origin  is  correct,  the  waters  of  the  few  alkaline  springs  in 
the  Lassen  Park  are  acid  at  some  point  or  points  nearer  their  source,  and  in  the 
process  of  rock  decomposition  they  have  become  alkaline  by  the  time  they  have 
reached  the  spring  vents.  The  close  relationship  of  these  springs  to  the  acid 
springs  in  composition  and  in  the  character  of  their  sediments,  as  well  as  the  absence 
of  other  important  differences,  lead  to  the  conclusion  that  all  are  of  the  same  age.5 

It  is  interesting  to  consider  how  other  investigators  have  handled  this  problem. 
Bunsen  concluded  that  the  alkaline  springs  of  Iceland  are  later  in  development  than 
the  acid  springs.  His  conclusion  is  based  on  chemical  evidence.  Elementary  sul¬ 
phur  is  apparently  regarded  by  Bunsen  as  the  only  original  sulphur  gas  in  the 
volcanic  emanations  there.  This  he  supposes  to  have  reacted  along  with  steam  on 
the  ferric  iron  of  the  pyroxenes  in  the  rocks,  with  formation  of  pyrite  and  sulphur 
dioxide,  as  previously  explained  in  another  connection  (p.  139).  In  the  course  of 
time  sulphur  dioxide  is  succeeded  by  hydrogen  sulphide  which  results  from  the 
action  of  steam  on  the  pyrite  previously  formed.  Bunsen  gives  observations  in 
support  of  his  statement  that  sulphur  dioxide  is  characteristic  of  an  earlier  phase  of 
volcanism  and  that  it  is  later  succeeded  by  hydrogen  sulphide.  His  explanation, 
however,  implies  that  steam  was  not  present  in  the  earlier  stage.  Neither  evidence 
of  this  fact  nor  any  reason  why  it  should  be  true  are  accorded  us.  Bunsen  says: 

In  consequence  of  these  changes  the  acid  reaction  of  the  water  with  which  the  rocks  are 
impregnated  is  converted  into  an  alkaline  reaction  resulting  from  the  formation  of  alkali 
sulphurets  at  the  cost  of  the  now  solely  reacting  sulphuretted  hydrogen  .  .  .  With  the 
disappearance  of  the  acid  reaction  begins  the  action  of  carbonic  acid  on  the  rocks  and  the 
formation  of  alkali  bicarbonates.  The  latter  dissolve  silica,  which  is  the  cause  of  the  forma¬ 
tion  of  geysers. 

Discussing  the  relation  of  acid  and  alkaline  springs  in  the  Yellowstone  Park, 
Hague6  affirms: 

The  ascending  waters  in  their  circuitous  course  penetrate  fresh  seams  and  cracks  in 
unaltered  rock  which  slowly  widen  under  the  disintegrating  influence  of  aqueous  vapor. 

1  Some  springs  in  the  Morgan  group  apparently  form  an  exception,  but  these  were  more  distant  from  the  volcanic  center, 
and  have  not  been  studied  by  the  authors. 

2  Liebigs  Ann.  62,  7,  1847. 

3  Bull.  Geol.  Soc.  Amer.  22,  116,  1911. 

4  Geol.  of  New  Zealand,  178,  1910. 

5  For  the  reason  previously  given  no  positive  statement  can  be  made  about  Morgan’s  Springs. 

6  Op.  cit.,  p.  1 18. 


168 


Finally  the  thermal  waters  following  these  cracks  issue  at  the  surface  as  hot  springs  and 
pools.  These  early  waters  are  usually  acid  in  composition  and  deposit  ferric  and  aluminous 
salts.  Occasionally  they  set  free  sulphur  derived  from  the  decomposition  of  hydrogen 
sulphide.  In  time  the  openings  through  which  they  flow  become  broader,  the  waters 
themselves,  free  from  hydrogen  sulphide,  become  clearer  and  neutral  and  at  last  issue  as 
siliceous  alkaline  waters. 

While  little  account  of  chemical  changes  is  taken  in  this  exposition,  one 
important  idea  stands  out  clearly;  the  alkaline  character  of  certain  of  the  springs 
of  the  Yellowstone  Park,  as  well  as  their  greater  size,  is  a  natural  result  of  pro¬ 
longed  rock  decomposition. 

On  the  other  hand,  Park1  believes  that  the  hot  acid  waters  of  New  Zealand  were 
originally  alkaline  and  that  they  have  subsequently  become  acid  through  chemical 
changes  occurring  near  the  surface  ol  the  ground.  Fie  says: 

Shafts  and  bore  holes  put  down  in  the  pumice  and  rhyolite,  which  constitute  the  great 
bulk  of  the  rocks  in  this  area,  have  shown  that  the  alkaline  waters  come  from  a  deep-seated 
source  while  the  acid  waters  have  quite  a  superficial  origin.  This  has  led  to  the  erroneous 
conclusion  that  all  the  waters  have  not  a  common  origin. 

On  p.  1 8 1  he  says: 

Of  the  genesis  of  the  ascending  alkaline  waters  nothing  is  known  at  present.  It  is 
not  improbably  magmatic. 

On  p.  180  we  read : 

The  hot,  ascending,  alkaline,  chlorinated  waters  become  partially  or  wholly  oxidized  into 
sulphates  by  contact  with  the  decomposing  iron  sulphide  with  formation  of  free  sulphuric 
and  hydrochloric  acids  and  the  liberation  of  sulphuretted  hydrogen  and  sulphurous  acid. 
In  this  way  the  ascending  alkaline  waters  that  happen  to  come  in  contact  with  masses  of 
pyrites  become  oxidized  in  the  superficial  layers  of  the  pumice  and  rise  to  the  surface  as 
neutral  or  acid  springs,  according  to  the  degree  of  oxidation  they  have  undergone. 

Whether  in  this  instance  there  is  sufficient  ground  for  supposing  that  the  acid 
waters  of  this  region  are  derived  from  the  oxidation  of  pyrite  is  not  clear  from  Park’s 
statement.  Evidence  in  general  is  certainly  against  it.  However,  the  views  of 
Park  probably  accord  with  the  views  of  many  economic  geologists  in  that  they 
regard  acid  waters  as  the  result  of  a  transformation  of  alkaline  waters  of  much 
deeper  origin.  At  the  famous  Steamboat  Springs,  Nevada,  the  authors  observed 
acid  salts  at  the  surface  of  the  ground  within  a  few  inches  of  alkaline  hot-spring 
waters.  Apparently  they  were  the  product  of  oxidation  of  hydrogen  sulphide  which 
had  escaped  from  the  waters.  At  Sulphur  Bank,  on  the  shore  of  Clear  Lake,  Cali¬ 
fornia,  the  deeper  ground  waters  have  been  shown  to  be  alkaline,  while  nearer  the 
surface  hydrogen  sulphide  and  sulphur  oxidize  to  sulphuric  acid,  which  has  been 
changing  the  rocks  to  silica.  In  neither  case  did  we  observe  alkaline  waters  chang¬ 
ing  to  acid  waters,  although  the  possibility  is  not  excluded. 

Pursuing  further  the  theory  which  we  have  advanced  regarding  the  relations 
of  acid  and  alkaline  springs,  it  becomes  clear  that  if  the  volcanic  gases  are  condensed 
under  conditions  unfavorable  to  the  oxidation  of  sulphur  gases,  the  water  would 


1  Geology  of  New  Zealand,  178-181,  1910. 


169 


become  alkaline  in  the  first  stages  of  rock  decomposition,  unless  the  gases  contain 
halogen  acids.  If  the  water  were  alkaline  in  the  begining  there  is  the  possibility 
that  it  might  become  subsequently  acid.  But  if,  as  observations  in  many  different 
places  seem  to  indicate,  alkaline  waters  are  characteristically  low  in  sulphur,  it 
would  be  only  in  the  very  first  stages,  if  at  all,  that  the  water  could  be  acid;  the 
amount  of  sulphur  would  be  insufficient  to  make  it  acid  at  any  subsequent  time, 
even  if  the  sulphur  were  completely  oxidized.  The  problem  is  one  that  calls  for 
detailed  observation  in  many  localities,  but  at  present  the  weight  of  the  evidence 
clearly  inclines  the  student  of  the  subject  to  the  conclusion  that  the  acid  hot  springs 
constitute  a  stage  of  volcanism,  logically  following  the  acid  fumaroles,  and  that  the 
alkaline  springs  develop  subsequently  as  a  necessary  result  of  the  processes  of  rock 
decomposition. 

Speaking  generally,  all  volcanic  hot  springs  in  the  lapse  of  time  should  become 
alkaline  as  a  result  of  the  gradual  decline  in  the  amount  of  sulphur  gases  and 
halogen  acids  in  the  volcanic  emanations  as  the  temperature  of  the  batholith  falls.1 
A  uniform  decline  would  not,  however,  explain  the  coexistence  of  acid  and  alkaline 
springs  in  the  same  area. 

Hague’s  argument  that  the  alkaline  springs  of  the  Yellowstone  are  older  be¬ 
cause  they  are  larger  is  a  plausible  one,  but  no  reason  is  given  for  the  change  in  the 
chemical  character.  The  large  springs  discharge  a  much  greater  volume  of  water, 
however,  and  there  is  some  reason  to  conclude  that  a  larger  proportion  of  it  is 
meteoric  than  is  true  of  the  acid  springs.  It  is  known  that  geysers  fill  with  cooler 
water  after  an  eruption,  and  it  is  easier  to  explain  the  heating  of  large  amounts  of 
surface  water  (p.  170)  in  a  given  area  than  to  explain  the  condensation  of  great 
quantities  of  magmatic  steam.  The  effect  of  dilution  on  the  acid  gases  is,  as  we 
have  found,  to  favor  the  formation  of  an  alkaline  water. 

There  is  another  reason  for  concluding  that  in  the  order  of  development  the 
alkaline  springs  follow  the  acid  springs,  as  Bunsen  and  Hague  believed.  The  prod¬ 
ucts  of  the  acid  hot  spring  are  all  soluble  or  easily  washed  away,  while  an  alkaline 
hot-spring  often  deposits  about  its  mouth  a  hard,  compact,  siliceous  sinter  quite 
refractory  toward  natural  acid  waters.  If,  therefore,  the  acid  springs  succeed  the 
alkaline  springs,  there  ought  to  be  many  instances  of  acid  springs  about  which  the 
surviving  sinter  tells  the  story  of  an  earlier  alkaline  age.  But  no  facts  of  this  sort 
are  on  record,  so  far  as  we  are  aware. 

This  conclusion  should  not  be  understood  to  imply  that  all  alkaline  springs  of 
volcanic  origin  must  be  originally  acid,  either  in  place  or  time.  According  to  our 
interpretation,  that  would  depend  on  the  nature  of  the  volcanic  gases.  If,  when 
the  springs  came  into  existence,  the  gases  contained  none  of  the  strongly  acid 
constituents  like  the  halogen  acids,  nor  constituents  which,  like  the  sulphur  gases, 
give  rise  to  strong  acids  through  oxidation,  the  waters  would  obviously  never  acquire 
an  acid  character,  and  the  processes  of  rock  decomposition  would  be  from  the  first 
of  quite  a  different  nature.  Whether  this  case  actually  occurs  in  nature  or  not  we 

1  This  statement  supposes  that  the  chemically  active  gases  disappear  before  the  steam.  It  is  supported  by  a  considerable 
body  of  evidence. 


170 


are  unable  to  say.  Thus  we  find  logical  grounds  for  the  conception  that  volcanic 
hot  springs  may  be  originally  alkaline,  or  originally  acid,  changing  later  to  alkaline, 
but  no  basis  for  the  conclusion  that  volcanic  springs  originally  alkaline  become  acid 
by  later  development. 

SUBSTANCES  OF  SECONDARY  ORIGIN  IN  VOLCANIC  HOT  SPRINGS. 

It  has  been  concluded  from  cogent  evidence  that  the  bases  in  the  Lassen 
spring-waters  are  derived  from  the  lavas  through  which  they  percolate,  but  from 
the  nature  of  the  gases  which  escape  from  the  springs  and  the  close  relation  which 
the  springs  bear  to  the  fumaroles  it  appears  equally  certain  that  the  sulphur  is 
derived  from  the  volcanic  gases.  It  has  also  been  implied  in  the  discussion  that  the 
sulphur,  halogens,  and  other  volatile  elements  in  all  volcanic  spring-waters  are 
similarly  derived,  but  in  view  of  the  great  diversity  of  conditions  which  prevail  in 
the  earth’s  crust  it  would  be  unwise  to  maintain  that  this  is  an  invariable  rule. 
If  waters  supplying  hot  springs  traverse  sedimentary  strata  in  which  soluble  salts, 
such  as  sulphates  and  chlorides,  have  been  segregated,  they  will  naturally  dissolve 
and  remove  a  portion  of  such  salts. 

In  this  connection  it  may  perhaps  be  inquired  why,  if  igneous  rocks  contain 
sulphur,  chlorine,  etc.,  these  elements  should  not  find  their  way  into  the  hot-spring 
waters  by  leaching  as  well  as  by  volatilization.  The  reply  is  that  whatever  is 
capable  of  passing  into  solution  in  the  course  of  the  decomposition  process  would 
necessarily  become  a  constituent  of  the  water,  but  the  amount  would  be  generally 
small.  For  example,  only  about  a  gram  of  lava  would  be  required  to  supply  all  the 
bases  in  a  liter  of  any  of  the  waters  of  the  Lassen  Park,  and  this  amount  would  not 
contain  more  than  a  few  milligrams  of  sulphur. 

The  Means  by  Which  Heat  is  Conveyed  to  the  Surface. 

If  we  accept  the  view  that  the  Lassen  hot  springs  contain  magmatic  water  and 
that  this  water  rises  from  the  magma  as  steam,  it  is  clear  that  the  condensation  of 
the  steam  would  supply  a  relatively  large  amount  of  heat.  Only  when  the  mag¬ 
matic  steam  is  very  hot,  where  it  meets  the  ground  water,  does  its  specific  heat 
become  comparatively  important.  Of  course,  the  other  volcanic  gases  participate 
in  the  heat  convection,  but  since  their  amounts  are  probably  very  small  when  com¬ 
pared  with  steam,  their  heat  capacities  being  only  about  half  as  great  as  that  of 
steam  (except  in  the  case  of  hydrogen  and  marsh  gas  which  are  insignificant  in  the 
Lassen  gases),  and  especially  since  they  do  not  undergo  a  change  of  state,  their 
contribution  to  the  heat  supply  is  negligible.  On  the  assumption  that  all  the  heat 
in  the  hot  springs  is  brought  up  by  magmatic  steam  and  that  none  is  lost  to  the 
surroundings,  some  estimate  of  its  limits  in  the  springs  and  fumaroles  can  be  made. 
The  highest  temperature  found  in  the  Park,  was,  as  previously  stated,  H7°C. 
The  temperature  ol  the  magmatic  steam  is  therefore  at  least  as  high.  The  boiling 
point  of  the  springs  in  this  particular  locality  (Bumpass  Hell)  is  910.  Taking  the 
temperature  of  the  surface  water  as  io°,  from  which  it  varied  little  during  the  time 
of  our  visits,  a  simple  calculation  shows  that  1  kg.  of  steam  in  condensing  would 
heat  about  6.9  kg.  of  surface  water  to  boiling  if  no  heat  were  lost  to  the  surrounding 
ground,  and  that  the  resulting  mixture  would  contain  about  12.5  per  cent  of  mag- 


171 


matic  water.  Under  the  above  conditions  this  would  be  the  lowest  possible  amount 
a  boiling  spring  could  contain.  If  the  temperature  of  the  magmatic  steam  were 
ioo°  hotter,  the  heat  supply  would  be  increased  about  io  per  cent,  but  the  magmatic 
water  in  the  mixture  would  be  lowered  thereby  less  than  i  per  cent  of  the  total  weight. 

Assuming  that  the  heat  of  the  springs  is  derived  from  magmatic  steam,  it  is 
obvious  that  the  above  figures  for  the  percentage  of  magmatic  water  would  have  to 
be  raised  in  consequence  of  the  loss  of  heat  to  the  ground  through  which  the  waters 
percolate.  After  a  time  an  equilibrium  would  be  established  in  which  this  loss 
would  be  equivalent  to  the  heat  loss  from  the  surface  of  the  ground  outside  the 
springs.  At  present  this  quantity  is  impossible  to  estimate.  Temperatures  at  the 
very  surface  in  the  hot-spring  areas  here  under  discussion  seem  to  be  near  the  nor¬ 
mal,  except  close  to  the  borders  of  the  pools.  A  few  feet  below  the  surface  the 
ground  is  often  quite  hot  for  long  distances  from  the  springs.  In  such  cases  steam 
always  seems  to  be  present.  We  are  inclined  to  the  conclusion  that  the  heat  lost  in 
this  way  is  less  than  that  carried  off  by  the  hot  water.  Still,  the  very  large  area  of 
the  surface  through  which  heat  escapes,  when  compared  to  the  area  of  the  springs 
themselves,  is  a  factor  which  may  raise  the  heat  loss  to  an  unsuspected  magnitude. 

But  there  are  facts  which  are  difficult  to  explain  by  the  assumption  that  vol¬ 
canic  heat  is  transmitted  to  the  surface  entirely  by  magmatic  steam.  For  example, 
there  is  strong  evidence  that  the  fumaroles  of  the  Katmai  region,  Alaska,  carry  with 
the  magmatic  gases  much  steam  originating  from  surface  water.  Gases  from  very 
hot  fumaroles  carry  sometimes  as  much  steam  in  proportion  to  the  other  gases  as 
those  several  hundred  degrees  lower  in  temperature.  To  assume  that  the  heat  is 
supplied  entirely  by  the  magmatic  steam  would  lead  to  an  absurdly  high  initial 
temperature  of  the  gases  and  of  the  magma.  But  if  the  water  is  not  all  magmatic 
one  must  assume  some  other  source  of  heat  to  vaporize  the  surface  water. 

Only  one  other  means  for  the  transfer  of  heat  from  a  batholith  to  the  surface 
has  yet  been  suggested,  so  far  as  we  are  aware,  namely,  conduction  through  the  rock. 
It  is  difficult  to  see  how  heat  could  be  conducted  through  the  rock  fast  enough  to 
keep  up  the  temperature  of  boiling  springs.  If  it  is  possible  at  all  it  must  be  accom¬ 
plished  by  the  circulation  of  the  water  through  a  labyrinth  of  cracks  and  crevices, 
which  brings  a  given  volume  of  water  into  contact  with  a  very  great  surface  of  rock, 
for  rock  is  a  poor  conductor  of  heat  at  the  best,  and  shattered  rock,  such  as  would  be 
expected  in  the  upper  strata  of  the  earth’s  crust  in  hot  spring  areas,  especially  poor.1 

Some  recent  experiments  of  Professor  Jaggar2  offer  good  evidence  that  at  least 
in  these  upper  strata  it  is  not  chiefly  by  conduction  that  heat  is  transferred.  In 
1922  Jaggar  sunk  several  drill  holes  in  or  near  the  crater  of  Kilauea.  One  of  these 
was  bored  in  the  bottom  of  the  crater  itself  within  a  mile  of  Halemaumau,  where 
a  high  temperature  gradient  was  expected.  At  a  depth  of  80  feet  a  temperature 
of  62°  C.  was  found.  As  a  matter  of  fact,  there  was  no  gradient  at  all  in  the  com¬ 
pleted  shaft;  the  temperature  was  equalized  by  a  rising  stream  of  volcanic  gases.3 

1  Thorkelsson  believes  that  ‘‘the  transmission  of  heat  from  the  interior  of  the  earth  takes  place  almost  exclusively  by 
means  of  convection  of  hot  water  and  steam  through  fissures  in  the  crust  of  the  earth.”  Mem.  de  1'  Acad.  roy.  de  Danemark  S, 
263,  1910. 

2  Bull.  Hawaiian  Volcano  Observatory  ic.  27.  63,  73.  97,.  III. 

3  That  the  gases  from  this  particular  bore  hole  were  volcanic  is  an  assumption.  1  hey  have  not  been  analyzed.  The 
gases  at  the  Sulphur  Banks  are  certainly  volcanic. 


The  maximum  temperature  found  in  any  of  the  bore  holes  (at  Sulphur  Banks 
outside  the  crater)  was  the  boiling-point  of  water,  96°  for  that  altitude. 

The  gases  here  are  mostly  steam,  96  to  9 7  per  cent  in  the  samples  analyzed, 
which  for  reasons  previously  stated  (p.  162)  is  doubtless  partly  magmatic.  But 
much  of  it  is  certainly  surface  water,  for  the  rainfall  there  is  abundant  and  the  lava 
is  remarkably  porous. 

Jaggar’s  experiments  therefore  tend  rather  to  confirm  our  ideas  of  heat  con¬ 
vection  by  steam,  and  they  suggest  further  that  surface  water  as  well  as  magmatic 
water  may  have  a  part  in  the  transfer.  Percolating  ground  water  receives  heat 
from  magmatic  steam  which  rises  through  crevices  cutting  the  path  of  the  former. 
Very  narrow  cracks  offer  a  ready  passage  to  the  steam,  but  are  less  accessible  to 
liquid  water.  We  may  suppose,  however,  that  some  surface  water  finds  its  way 
through  and  into  a  zone  where  it  is  not  stable,  but  where  the  temperature  may  or 
may  not  be  much  above  boiling  according  to  varying  conditions  in  different  places. 
For  every  point  in  the  path  of  the  percolating  ground  water  there  is  of  course  a 
depth  below  which  gravity  can  not  bring  it  again  to  the  surface.  If  the  water  falls 
below  this  depth  it  will  continue  to  fall  until  it  is  vaporized,  when  it  will  again  rise. 
In  this  way  another  portion  of  heat  may  be  transferred  from  the  rock  to  the  surface 
water.  This  process  seems  the  more  likely  to  happen  because  it  is  difficult  to 
believe  that  fractured  rock  which  permits  the  passage  of  steam  would  not  also  give 
access  to  some  liquid  water,  though  in  particular  cases  it  is  possible  that  the  pressure 
of  escaping  steam  might  practically  prevent  it.  One  limitation  to  the  transfer  of 
heat  by  this  means  is  obvious.  Since  the  heat  is  withdrawn  from  the  rock  for  the 
most  part  by  a  change  of  state  in  the  water,  it  can  not  be  operative  below  the  depth 
which  liquid  water  can  reach.  From  the  magma  or  batholith  up  to  that  level  it 
would  seem  that  heat  conduction  must  afford  the  only  means  of  transferring  heat 
except  that  of  magmatic  steam.  As  to  the  reheated  fraction  of  ground  water  which 
may  be  instrumental  in  the  transfer  of  heat,  it  is  clear  from  the  previous  discussion 
that  only  a  comparatively  small  proportion  would  be  required  to  heat  all  of  the 
remainder  to  boiling,  even  if  there  were  no  magmatic  steam  at  all. 

The  minimum  limit  to  the  amount  of  magmatic  water  which  a  boiling  spring 
may  theoretically  contain  is  therefore  subject  to  two  corrections.  In  so  far  as  heat 
from  the  magmatic  steam  is  lost  to  the  surrounding  ground,  the  limit  must  be  raised, 
while  in  so  far  as  ground  water  is  vaporized  and  thus  participates  in  the  convection 
of  heat,  the  limit  must  be  lowered.  At  present  we  can  not  estimate  the  magnitude 
of  either  correction,  but  we  are  inclined  to  the  view  that  the  latter  is  the  greater. 
Whenever  the  magmatic  water  in  a  spring  falls  below  the  minimum  limit  in  question 
the  temperature  of  course  would  fall  below  boiling.  On  the  other  hand,  if  the 
amount  of  the  ground  water  diminishes,  the  spring  will  boil  more  and  more  violently 
as  the  proportion  of  magmatic  steam  increases.  Spouting  will  result,  and  since 
the  temperature  can  not  rise  as  long  as  liquid  water  remains,  the  new  accession  of 
heat  will  be  chiefly  expended  in  evaporation,  until  finally,  when  the  steam  has 
reached  a  sufficient  excess,  a  fumarole  will  result.  This  phenomenon  has  been 
observed  both  in  mud  pots  and  in  hot  springs.  The  transformation  of  certain 


173 


boiling  springs  at  the  Boiling  Lake  into  fumaroles  in  midsummer  of  1923  is  an 
especially  illuminating  observation  (p.  155). 

It  is  a  very  interesting  fact  that  nearly  all  the  fumaroles  in  the  Lassen  Park 
have  almost  the  same  temperature  as  the  hottest  springs,  which  is  practically  that 
of  boiling  water  for  the  elevation.  There  are  many  such  fumaroles  at  Katmai,  at 
Kilauea,  and  no  doubt  elsewhere.  The  most  satisfactory  explanation  of  this 
phenomenon  is  that  there  is  liquid  water  in  contact  with  the  steam  of  these  fuma¬ 
roles,  equilibrium  with  which  controls  the  temperature  as  it  does  in  the  boiling 
process.  In  some  fumaroles  we  had  ocular  evidence  of  the  fact,  and  there  was  other 
evidence  in  certain  instances.  The  maximum  amount  of  magmatic  steam  which 
such  a  fumarole  can  contain  will  depend  of  course  on  the  conditions.  Assuming,  as 
before,  that  the  magmatic  steam  where  it  meets  the  ground  water  has  a  temperature 
of  1 1 70,  that  the  temperature  of  the  surface  water  is  io°,  and  the  boiling-point  910, 
we  calculate  that  an  amount  of  ground  water  (supposing  it  to  evaporate)  equal  to 
about  2  per  cent  of  the  weight  of  the  steam  would  be  required  to  cool  it  to  91  °,  and 
the  mixture  of  course  would  contain  nearly  the  same  percentage  of  steam  of  surface 
origin.  Only  a  small  excess  of  surface  water  would  theoretically  be  required  to 
maintain  the  boiling  temperature.  The  amount  of  surface  water  required  to  cool 
the  steam  to  the  boiling-point  varies  considerably  with  the  initial  temperature  of  the 
latter,  since  steam  is  not  condensed  in  the  process.  If  the  steam  were  ioo°  hotter 
(2170)  the  surface  water  required  would  amount  to  9.7  per  cent  of  the  weight  of  the 
steam  and  there  would  be  8.8  per  cent  steam  of  surface  origin  in  the  vapor  mixture. 
If  we  take  into  account  the  fact  that  the  ground  would  aid  in  the  cooling  of  the 
steam,  we  see  that  the  surface  water  required  would  be  somewhat  less  than  these 
limits.  But  if,  as  we  believe  probable,  surface  water  participates  in  the  convection 
of  heat,  probably  a  larger  correction  in  the  opposite  direction  would  be  required. 
Fumaroles  of  the  temperature  of  boiling  water  are  therefore  likely  to  contain 
less  magmatic  water — perhaps  much  less  than  the  theoretical  upper  limit.  From 
a  physical  standpoint  there  would  be  no  essential  difference  between  a  fuma¬ 
role  of  this  nature  and  a  boiling  hot  spring  except  in  the  relative  amounts  of  the 
liquid  and  vapor  phases.  So  long  as  conditions  permit  water  to  flow  from  the  vent 
the  phenomenon  would  be  called  a  spring.  In  the  fumaroles  the  water  level, 
where  there  is  one,  must  be  below  ground,  but  the  level  may  be  rising  or  falling,  or 
practically  constant,  with  the  water  flowing  out  at  a  level  lower  than  the  orifice. 

The  hypothesis  of  heating  by  magmatic  steam  implies  that  the  amount  of 
magmatic  water  in  springs  and  fumaroles  varies  from  place  to  place  and  from  time 
to  time  in  the  same  spring.  The  limits  are  not  ascertainable  at  present,  but  the 
discussion  indicates  that  they  are  wide  apart.  In  the  time  of  melting  snow,  at  any 
rate,  .all  the  evidence  goes  to  show  that  ground  water  is  in  large  excess,  and  it  is 
altogether  probable  that  the  amount  decreases  with  the  advancing  season,  but  as 
the  fumaroles  themselves  may  contain  much  steam  of  surface  origin,  only  a  theoret¬ 
ical  upper  limit  to  the  amount  of  magmatic  water  can  be  set,  and  this  may  be  much 
above  the  actual. 

In  view  of  the  fact  that  much  has  been  said  in  the  foregoing  pages  regarding  the 
participation  of  meteoric  water  in  the  activities  both  of  the  volcano  and  of  the  adjacent 


174 


hot  springs,  it  is  appropriate  to  consider  briefly  how  such  waters  reach  the  centers  of 
activity;  what  is  the  manner  and  what  the  limitations,  if  any,  of  their  circulation. 

In  the  consideration  of  this  question  capillary  forces  continue  to  be  invoked 
as  they  have  been  always  since  Daubree  showed  that  these  forces  under  given  con¬ 
ditions  were  competent  to  move  water  against  the  opposing  force  of  gravity  or  an 
adverse  gas  or  vapor  pressure.  In  point  of  fact,  these  “given  conditions”  prescribe 
limitations  which  are  absolutely  prohibitive  to  any  extended  application  of  the 
principle  to  such  geological  phenomena  as  those  here  considered.  This  has  been 
conclusively  shown  by  Johnston  and  Adams  1  and  plainly  indicated  by  Kemp2  and 
by  Osmond  Fisher  3  much  earlier.  Capillarity  is  strictly  a  force  of  surface  tension; 
“a  column  of  liquid  can  be  supported  only  when  there  is  a  free  liquid  surface  within 
the  capillary.”  4  “Capillary  action  can  be  made  to  do  great  things,  .  .  .  But  it 
can  not  cause  a  liquid  to  flow  continuously  through  a  tube,  however  short;  for,  if 
it  could,  it  would  give  us  perpetual  motion.”  5  Moreover,  the  surface  tension 
diminishes  as  the  temperature  rises,  and  of  course  vanishes  when  the  surface  van¬ 
ishes  at  the  boiling  temperature.  It  is  therefore  of  no  service  in  accounting  for  the 
access  of  water  to  a  volcano  conduit  or  to  a  boiling  spring.  It  is  perhaps  of 
importance  in  facilitating  the  surface  evaporation  of  giound  waters  in  a  hot-spring 
area. 

Johnston  and  Adams  have  also  considered  the  magnitude  to  which  capillary 
forces  can  attain  in  support  of  the  geological  speculation  that  the  penetration  of 
water  into  deep-seated  rocks  can  be  accounted  for  in  this  way.  The  principle 
invoked  is  that  the  pressure  developed  by  capillarity  increases  as  the  pore  spaces 
diminish  in  size.  They  discover  at  once  that  such  pressures  are  “insignificant  in 
comparison  with  the  hydrostatic  pressure  except  for  very  fine  pores,”  and  as  soon 
as  the  pores  are  fine  enough  (o.i  n  or  o.oi  n  in  diameter),  the  amount  of  water  which 
could  flow  through  them,  assuming  a  total  pore-space  of  io  per  cent,  would  be 
respectively  0.15  or  0.0015  c-  cm-  Per  year  f°r  each  centimeter  of  surface. 

Johnston  and  Adams  leave  no  doubt  of  the  conclusion  to  be  drawn  from  this 
full  and  complete  investigation  of  the  matter;  they  say  in  their  resume  (op.  cit.  p.  1 5) : 

Capillary  forces  are  effective  only  when  there  is  a  surface  of  separation  within  the  pores; 
moreover,  they  diminish  steadily  with  rise  of  temperature  and  vanish  at  the  critical  point 
of  the  liquid.  Calculation  shows  that  the  effects  producible  at  any  considerable  depth  are, 
in  comparison  with  the  pressure  due  to  the  hydrostatic  column,  insignificant  except  in  pores 
of  such  fineness  that  the  amount  of  water  which  could  flow  through  them  is  infinitesimal. 

This  conclusion  leaves  the  movement  of  meteoric  water  in  the  ground,  and  so 
its  approach  to  centers  of  volcano  and  hot-spring  activity,  subject  primarily  to  the 
action  of  gravity  and  the  local  temperature  relations.  The  penetration  of  liquid 
water  to  considerable  depths  is  therefore  dependent  upon  the  existence  of  actual 
cavities,  or  structural  discontinuities,  and  is  limited  in  depth,  so  far  as  can  be  in¬ 
ferred  from  our  present  knowledge,  to  the  zone  in  which  such  structural  discon- 

1  John  Johnston  and  L.  H.  Adams,  Observations  on  the  Daubree  experiment  and  capillarity  in  telation  to  certain  geo¬ 
logical  speculations,  Journ.  Geol.  22,  8,  1914. 

2  J.  F.  Kemp,  Role  of  Igneous  Rocks  in  the  Formation  of  Veins,  Frans.  Am.  Min.  Eng.  31,  177,  1901. 

;i  Osmond  Fisher,  Physics  of  the  earth’s  crust,  2d.  Ed.,  p.  143,  1889. 

4  Johnston  and  Adams,  op.  cit. 

5  Osmond  Fisher,  op.  cit. 


175 


tinuities  can  occur — sometimes  described  as  the  “zone  of  fracture.”  Above  the 
boiling-point  or  critical  temperature  the  penetration  of  water  vapor  is  governed 
entirely  by  the  mechanics  of  gas  pressure  and  movement  and  the  solubility  or 
chemical  activity.  The  observations  presented  in  the  preceding  pages  contain 
abundant  evidence  ot  the  solubility  ol  water  vapor  in  silicate  solutions  (magmas) 
and  of  the  enormous  pressures  which  may  be  developed  locally  under  given  condi¬ 
tions  (p.  72  et  seq.). 

All  of  these  observations  tend  definitely  to  restrict  in  depth  the  zone  in  which  both 
hot-spring  and  volcanic  activity  can  occur  and  bring  us  more  and  more  definitely  to 
the  conclusion  that  these  phenomena  are  subject  to  local  rather  than  general  condi¬ 
tions  and  have  no  far-reaching  subsurface  connections  or  very  deep-seated  origin. 

CONCLUSION. 

As  a  result  of  this  investigation  in  the  Lassen  National  Park  it  is  concluded 
that  the  hot  springs  in  this  locality  are  chiefly  fed  by  surface  water  which  drains 
the  basins  in  which  they  lie,  and  that  the  variation  in  the  volume  of  the  water  locally 
and  seasonally  accounts  for  the  variation  in  volume  and  partly  for  the  variation  in 
temperature  which  we  find  in  the  springs.  Another  portion  of  water  is  derived  from 
an  underlying  batholith.  Arising  in  the  form  of  steam  along  with  other  volcanic 
gases  though  clefts  in  the  rock,  it  is  condensed  by  the  ground  waters  and  becomes 
mingled  with  them.  The  amount  of  this  magmatic  water  varies  in  different  springs 
and  at  different  times  in  the  same  spring,  not  so  much  because  of  inconstancy  in 
the  emanation  as  because  of  variations  in  the  volume  of  ground  water.  In  the  time 
of  melting  snow  the  magmatic  water  is  in  general  small  in  amount.  It  increases  as 
the  ground  water  diminishes.  The  final  stage  which  is  sometimes  actually  realized 
is  a  fumarole.  The  fumaroles  of  the  Lassen  region,  whether  persistent  or  otherwise, 
have  almost  always  a  temperature  close  to  that  of  boiling  water  for  the  elevation. 
This  is  interpreted  to  mean  that  there  is  liquid  water  below  ground  in  contact  with 
the  steam. 

Some  of  the  heat,  perhaps  the  larger  part  of  it,  is  derived  from  the  magmatic 
steam.  Another  portion  conveyed  by  conduction  through  the  lower  depths  of  the 
rock  is  carried  through  the  upper  strata  by  the  evaporation  of  a  fraction  of  the 
ground  water  in  a  manner  which  has  been  explained.  This  process  may  become 
relatively  important  where  the  quantity  of  ground  water  is  especially  great. 

Whether  the  spring  waters  descend  throughout  their  whole  course,  or  whether 
they  ascend  in  the  latter  part  of  it  as  artesian  waters,  we  do  not  know,  but  according 
to  our  view  the  liquid  water  is  moved  by  gravity  alone  and  comes  from  no  greater 
depth  than  that  to  which  the  ground  water  penetrates,  while  the  mineral  content, 
excepting  the  volatile  portion  or  portions  formerly  volatile,  is  all  derived  from  the 
rock  above  that  level. 

The  hot  springs  of  acid  character  are  closely  related  to  fumaroles  which  give  off 
sulphur  gases  or  in  other  localities  halogen  acids.  The  alkaline  springs  are  a  later 
development  from  acid  waters  in  the  process  of  rock  decomposition.  Under 
favorable  conditions  the  acid  is  exhausted  and  the  further  action  of  hot  water  on 
the  rock  (hydrolysis  of  alkali  silicates)  gives  the  water  an  alkaline  character. 


APPENDIX. 

List  of  Observed  Eruptions  of  Lassen  Peak  1914-1917.1 

Observers.  Stations. 

F — Forest  Service . Summer,  Brokeoff  Mt.,  4  miles  west; 

Winter,  Mineral,  15  miles  south. 

0 — George  W.  Olsen . Chester,  20  miles  east. 

D — Miss  Dines  (Postmistress) . Manton,  20  miles  west. 


.  No: 
Eruption. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

1914. 

M  inutes 

1. . . . 

F,  O.  .  .  . 

May 

30 

5h  p.m. 

10 

Heavy.  H.  Abbey  reports  size  of  crater  25  bv 

40  feet. 

2 . 

F,  O. . . . 

June 

1 

8h  a.m. 

15 

Heavier. 

3 . 

F . 

U 

2 

9h30m  a.m. 

30 

Very  heavy. 

4 . 

F,  0  . . . . 

u 

8 

4h30m  p.m. 

40 

Heavier. 

5. . . . 

F . 

u 

9 

10h30m  a.m. 

30 

Heavy,  steam  darker. 

6. .  . . 

0... 

u 

12 

10h45m  a.m. 

7 .... 

F . 

a 

12 

3h45m  p.m. 

50 

Heavy,  steam  very  dark.  Size  of  crater  40  bv 

100  feet. 

8 . 

F,  0. . 

u 

13 

6h  a.m. 

30 

Heavy.  Ashes  fell  at  Mineral. 

9 . 

0 . 

u 

13 

3h45m  p.m. 

10 . 

F . 

a 

14 

6h  a.m. 

? 

Unconfirmed.  Reported  bv  Red  Bluff. 

11 . 

F,  O. . . 

u 

14 

9h43m  a.m. 

30 

Heaviest  yet.  Altitude  of  smoke  2,5000  ft. 

12 . 

F,  0  . 

u 

14 

6h45m  p.m. 

is 

Medium.  Size  of  crater  450  bv  125  feet. 

13 . 

F . 

u 

19 

8h15m  p.m. 

15 

Medium.  Altitude  of  smoke  2,000  feet.  Size  of 

crater  600  bv  150  feet. 

14 . 

0 . 

a 

22 

7h30ra  p.m. 

15 . 

F . 

a 

29 

3b  a.m. 

? 

New  snow  covered  bv  layer  of  ash. 

16 . 

F,  0. . . . 

(( 

30 

llh06m  a.m. 

Heavy.  Series  of  slight  eruptions  followed 

first.  Continued  to  5  p.  m.  Altitude  2,800 

feet. 

17 . 

F,  0  . 

July 

1 

5h30m  a.m. 

50 

Heaviest  yet.  Altitude  5,900  feet. 

18 . 

0. ... 

a 

1 

2h20m  p.m. 

19 . 

F,  0.  . 

a 

2 

6h50m  p.m. 

30 

Very  heavy. 

20 . 

F . 

u 

6 

3h30m  a.m. 

30 

Reported  bv  Red  Bluff.  Heavy  steam  and 

smoke  from  entire  length  of  crater. 

21 . 

F . 

u 

13 

3h07m  p.m. 

40 

Medium.  Aircalm.  1  hin  column  steam  rose  to 

height  of  1,800  feet.  Little  ash  visible.  West 

end  of  crater 

22 . 

F.... 

a 

15 

6h05ra  a.m. 

Very  heavy.  Of  long  duration.  4  hours. 

23 . 

F... . 

u 

15 

12h05m  p.m. 

Entire  afternoon. 

Greatest  disturbance  yet,  exceeding  previous 

eruptions  in  intensity  and  duration.  Great 

amount  ash  thrown.  Height,  8,910  feet. 

24 . 

F. . . 

a 

16 

12h30m  p.m. 

Very  heavy.  Volcanic  dust  fell  at  Mineral. 

through  early 

hours. 

25 . 

F . . . . 

a 

16 

4h30m  a.m. 

Several  hours. 

Heavy  eruption. 

26 . 

0 . 

u 

16 

6h  a.m. 

27 . 

0 . 

u 

16 

12h  M 

28 . 

F . 

a 

17 

6h  a.m. 

Heavy  eruption.  Volcanic  ash  fell  at  Mineral 

29 . 

F.... 

a 

17 

1  lh47m  a.m. 

Heavy  eruption 

30 . 

F,  0 

u 

18 

5h28m  a.m. 

By  far  most  violent  eruption  to  rlate  Ash, 

steam,  etc.,  rose  to  height  of  11,000  feet. 

31 . 

F,  0 . 

Aug. 

10 

5h30m  p.m. 

Continued  after 

Medium.  Small  quantity  of  ash  thrown  out. 

dark 

32 . 

F,  0 . 

u 

19 

7h24m  a.m. 

4  hours,  30  minutes. 

Very  heavy.  Huge  clouds  of  ash  thrown  out. 

Height  10,500  feet. 

33 ... . 

0. . 

a 

20 

5h  a.m. 

34 . 

F,  0 . 

u 

21 

1  lh10m  a.m. 

1  hour,  40  minutes. 

One  of  the  largest  eruptions  to  date.  Entire 

crater  active.  Height  10,560  feet. 

35 . 

F,  0 . 

u 

22 

8h40m  a.m. 

Heavv  ash  column  shot  up  obliquely  instead  of 

vertically  as  in  all  former  eruptions.  Alti- 

tilde,  7,590  feet. 

36 . 

F,  0 

a 

22 

12h40m  p.m. 

1  hour,  20  minutes. 

Heavy.  Entire  crater  active.  Height  5,940  feet. 

37 . 

F,  0 . 

u 

22 

4h35ra  p.m. 

55  minutes. 

Medium.  Short  duration.  Altitude  6,000  feet. 

38 . 

F,  0 . 

u 

23 

6h33m  a.m. 

1  hour,  53  minutes. 

Medium.  Height  5,610  feet. 

1  Collected  by  J.  S.  Diller. 


176 


177 


No. 

Eruption. 

Authority. 

Date. 

Time. 

Duration. 

1914 

Minutes 

39 . 

F,  O . 

Aug.  23 

7h43m  p.m. 

Continued  after 

dark. 

40 . 

F,  O . 

Sept.  5 

12h23m  p.m. 

4  hours. 

41 . 

F . 

“  5 

4h25m  p.m. 

1  hour,  35  minutes. 

42 . 

F,  O . 

“  6 

1  lh  4m  a.m. 

3  hours,  55  minutes. 

43 . 

F . 

“  7 

10h30m  p.m. 

Continued  indefin- 

itely  thru  early 

morning  hours. 

44 . 

F . 

“  8 

8h  a.m. 

Had  not  reached 

normal  when  sec- 

ond  eruption  took 

place. 

45 . 

F,  O 

“  8 

9h55m  a.m. 

Normal  had  not 

been  reached  when 

third  eruption  of 

day  took  place. 

46 . 

F... 

«  8 

10h25m  a.m. 

Normal  not  reached 

47 . 

F. . . 

«  8 

1  1  a.m. 

1  hour,  50  minutes. 

48 . 

F,  O . 

“  9 

4h20m  a.m. 

49 . 

F,  O  . 

“  9 

3h  p.m. 

Continued  after 

sundown. 

50 . 

O . 

“  10 

5h  a.m. 

51 . 

O . 

“  11 

4h30m  a.m. 

52 . 

O . 

“  15 

8h  p.m. 

53 . 

F . 

“  16 

3h  p.m. 

Unknown. 

54 . 

F . 

“  10 

3h10m  a.m. 

Short. 

55 . 

O . 

“  20 

12h30m  a.m. 

56 . 

F . 

“  20 

a.m 

5  hours 

57 . 

F,  O  . 

“  20 

1  1  h.S.Sm  a.m. 

3  hours. 

58 . 

F,  O . 

“  ?l 

6h  5m  a.m. 

59 . 

F,  O  .... 

“  29 

7h15m  p  m. 

. 

• 

60 . 

F . 

“  30 

10h  p.m. 

3  hours. 

61 . 

E,  O . 

Oct.  1 

5h15m  a.m. 

1  hour. 

1 

Intensity  and  Remarks. 


Larger  than  morning  disturbance.  Height 
5,940  feet. 

Medium.  Full-length  crater  active.  Height 
5,600  feet.  Size  of  crater  605  by  208  feet. 
(C.  H.  Lee’s  measurement). 

Medium.  Larger  quantities  of  ash  than  morn¬ 
ing  eruption.  Height  4,950  feet. 

Medium.  Entire  crater  active.  Height  5,920 
feet.  (Crater  reported  to  have  widened  con¬ 
siderably  in  west  end.) 

Very  heavy.  Wind  negligible,  column  dust  as¬ 
cended  to  great  height.  Rumblings  awakened 
lookout  on  Brokeoff  Mountain. 

Very  slight.  Began  subsiding  almost  immedi¬ 
ately  after  first  outburst. 


Medium.  Began  subsiding  immediately  after 
outburst. 


Medium.  Slightly  more  ash  thrown  out  than 
two  preceding  eruptions. 

Heavy.  Ash  clouds  enveloped  mountain.  En¬ 
tire  crater  active. 

Medium. 

Considered  one  of  the  largest  eruptions  to  date. 
Heavy  fall  of  ashes  in  Mineral  and  Lyons- 
ville. 


At  8  p.m.  on  Sept.  15,  people  in  Warner 
Valley  heard  rumbling  noises  and  felt  a 
slight  earthquake.  Not  noticed  at  Chester. 

Mt.  obscured  by  clouds.  Only  indication  of 
eruption  was  fall  of  ashes  at  Viola.  Storm 
cleared  on  18th,  disclosing  3  new  vents  on 
west  slope,  undoubtedly  caused  by  eruption 
of  16th. 

Medium. 

The  ground  here  was  white  with  the  dust  from 
the  eruption  at  12.30  a.m.,  the  only  time  it 
has  fallen  here  (Chester). 

Very  heavy.  Accompanied  by  terrific  rumbl¬ 
ings,  followed  by  heavy  vibrations.  No 
change  noted  in  vents. 

Heavy.  Rumblings  and  detonations  heard  at 
Mineral  for  first  time.  Ashes  fell  at  Mineral. 
No  change  noted  in  vents. 

Probably  most  violent  eruption  to  date.  Ash 
practically  obscured  sky  from  Mineral  view¬ 
point.  Vent  nearest  top  on  west  slope  con¬ 
siderably  enlarged.  Equal  volumes  of  steam 
from  both  sides  of  mountain.  No  mutter- 
mgs  heard  or  earthquake  felt  at  Chester. 

F  —  “Very  heavy.  Luminous  bodies  hurled 
high  into  air.  Substantiated  by  Turner  Mt. 
Lookout  and  other  eyewitnesses.  Demol¬ 
ished  lookout  house.  Estimated  length  of 
crater  900  feet.  Considerably  widened.  Be¬ 
coming  more  rounded  with  each  eruption.” 

O —  “The  only  time  I  saw  light  was  a  flash  of 
light  that  looked  as  tho  it  might  have  been 
an  explosion  of  gases  or  an  electric  flash. 
This  is  the  only  eruption  I  have  seen  at 
night.” 

Heavy.  Ashes  fell  at  Hall’s  Plat. 

Heavy. 


178 


^  No. 
Eruption. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

1914 

Minutes 

62 . 

F,  0 . 

Oct. 

1 

71'  a.m. 

2  hours. 

Medium. 

63 . 

F.  0 . 

a 

1 

12  M 

1  hour. 

Medium. 

64 . 

0 . 

u 

1 

4h40m  p.m. 

65  . 

0 . 

u 

6 

6h10m  a.m. 

Estimated  height  of  column  8,000  feet.  Color 
at  first  very  dark,  later,  turning  almost 

to 

1  lh30m  p.m. 

white. 

66 . 

F . 

u 

7 

6h20m  a.m. 

4  hours. 

Very  heavy. 

Made  a  trip  to  the  top  of  the  Mountain  Oct.  1 1 . 
The  crater  is  much  wider  and  deeper  than  at 

67  &  68 

0 . 

u 

10 

? 

my  last  visit  July  19.  I  guessed  the  crater  to 
be  between  400  and  500  feet  wide  and  700  and 

800  feet  long  and  150  and  200  feet  deep.  For¬ 
est  outlook  house  demolished  by  large  quan¬ 
tity  of  stones  blown  out  since  Sept.  15.  The 
crater  has  cut  through  the  West  Butte  and 
there  is  a  large  crack  extending  down  the  west 
side  of  the  Mountain  for  several  hundred  feet. 

emitting  steam  constantly- 

69  ... 

0 . 

a 

15 

3h  a.m. 

70 

0 . 

u 

15 

9h30m  p.m. 

Fire  being  seen  at  this  eruption  but  not  bv  my¬ 
self. 

71 . 

0 . 

u 

16 

4h30m  a.m. 

72.  . 

F . 

u 

17 

Between  8 

Unknown. 

Unknown.  Observed  by  parties  in  vicinity  of 
mountain. 

p.m.  &  Mid- 

night. 

73 . 

F,  0 . 

u 

22 

1  lh30m  a.m. 

2  hours. 

F — “Very  heavy.  Air  at  Mineral  darkened  by 
heavy  fall  of  ash.” 

O — “Rumbling  plainly  heard  here  at  Chester 
but  no  earthquake  felt.  Yori  says,  Oct.  22, 
biggest  eruption.  He  ascended  Lassen  Peak 

soon  after  and  states  that  the  ashes  were  so 

hot  he  could  not  remain  long  at  one  place  and 
that  the  dog’s  feet  were  burned.  He  took  a 
photo  of  the  new  crater  on  the  N.  E.  side  at 
the  head  of  Lost  Creek.” 

74 . 

F,  0 . 

u 

23 

6'T5,n  a.m. 

1  hour. 

F — “  Heavy.  Snow  on  all  sides  of  mountain 
covered  bv  ash.” 

75  &  76 

0 . 

tc 

23 

6h10,n  p.m. 

“There  were  numerous  flashes  of  light  seen  at 
this  eruption.  There  seems  to  be  no  doubt  as 

77 . 

I  have  talked  to  several  eyewitnesses  whom  I 
believe  to  be  reliable  and  all  are  positive  that 
it  was  light  from  the  volcano  and  not  from  the 
rays  of  the  setting  sum.  Unfortunately  I  did 
not  see  this  eruption.” 

() . 

u 

27 

lh50m  p.m. 

Oct.  26,  ascended  the  mountain  and  found 
the  crater  quite  a  bit  deeper. 

78 . 

0,  D . 

u 

28 

2h  p.m. 

79 . 

F,  D . 

a 

30 

lh30m  p.m. 

20  minutes. 

F — “Occurred  during  storm.  No  further 

details.” 

80 . 

0.  I) . 

a 

31 

llh50m  a.m. 

81 

0 . 

Nov. 

1 

6h  p.m. 

8h45m  a.m. 

82 . 

0 . 

« 

2 

15  Minutes. 

83 ...  . 

0 . 

a 

2 

9h  5m  a.m. 

10  Minutes. 

84 . 

F,  D . 

a 

2 

10h10m  a.m. 

30  Minutes. 

F — “  Medium.” 

D — “Smoke  .  .  .  south.” 

85  .  . 

F . 

u 

2 

2 

12h10,n  p.m. 
4h20m  p.m. 

30  Minutes. 

Medium. 

F — “Medium.”  D — “Smoke  .  .  .  south.” 

86 . 

F,  0,  D.. 

u 

20  Minutes. 

87 . 

0 . 

u 

3 

2h15'n  a.m. 

Seen  by  a  neighbor. 

Steaming  or  smoking  nearly  all  day. 

88 . 

0 . 

u 

4 

? 

89 . 

1) . 

10 

4h25m  p.m. 

90 . 

0 . 

u 

11 

? 

Heavy  clouds  of  steam  rising  from  the  crater 

91 . 

0 . 

3h  p.m. 

all  day  but  not  like  the  regular  eruptions. 

(( 

12 

Same  as  on  Nov.  11,  with  small  eruption  at  3 
p.m.  Did  not  rise  above  the  mountain. 

Drifted  north. 

92 . 

F . 

u 

16 

10h10m  a.m. 

30  Minutes. 

Slight. 

179 


No.- 

Eruption.  I 


Authority.  Date. 


1914 


Duration. 


Intensity  and  Remarks. 


Minuta 


93. 


O. 


Nov.  18 


2h50™  p.m. 


94 . 

F . 

a 

18 

4h10m  p.m. 

20  Minutes. 

95 . 

D . 

u 

20 

96 . 

F...  . 

Dec. 

3 

During 

Unknown. 

afternoon. 

97 . 

F . 

U 

11 

3h30m  p.m. 

Unknown. 

98 . 

F . 

U 

12 

llh45m  a.m. 

30  Minutes. 

99 . 

F,  O . 

U 

12 

4h45m  p.m. 

40  Minutes. 

100 . 

F . 

U 

13 

10h30m  a.m. 

101 . 

O . 

U 

15 

? 

102 . 

0 . 

U 

15 

lh  p.m. 

103 . 

0 . 

u 

16 

? 

104 . 

0... 

u 

17 

llh  a.m. 

105  . 

0. . . . 

u 

18 

3h  to  4h  p.m. 

106 . 

0 . 

u 

18 

? 

107 . 

O.  D. . . . 

u 

24 

1 1  h45m  a.m. 

108 

O.... 

u 

27 

7'1  a.m. 

109 

O . 

u 

29 

110 

0  . 

u 

31 

1915 

111 . 

D . 

Jan. 

2 

4h55m  p.m. 

10  minutes. 

112 . 

F . 

U 

13 

6h  a.m. 

Unknown. 

113 . 

D . 

U 

17 

5h30m  a.m. 

hour. 

Small  eruption. 

Note. — Since  Nov.  26  (letter  of  Dec.  7)  there 
has  been  a  heavy  fall  of  snow  in  the  high 
mountains,  I  should  judge  about  4  feet, 
there  being  2  feet  at  this  place  (Chester). 
During  this  time  (Nov.  26  and  Dec.  7)  I 
have  seen  Mt.  Lassen  but  twice.  On  Nov. 
30  the  clouds  cleared  away  and  Lassen  was 
plainly  visible  for  several  hours,  and  it  was 
completely  covered  with  ashes  showing  that 
there  had  been  a  heavy  eruption  within  the 
last  24  hours,  otherwise  it  would  have  been 
white.  At  that  time  there  were  two  or  three 
feet  of  snow  on  the  high  mountains.  Dec.  4 
it  was  partly  visible  for  a  short  time.  At 
that  time  it  was  white. 

Medium.  Several  parties  viewing  eruption  from 
different  angles  declared  disturbance  came 
from  north  slope  of  mountain. 

Eruption  at  night. 

Mediu  m. 

Reported  as  heavy  snowstorm  on  mountain  at 
time  of  eruption. 

Slight. 

F — “  Medium.” 

O — “Rays  of  setting  sun  colored  this  eruption 
hut  nothing  like  fire  was  noticed.” 

Medium. 

At  daylight  steam  rising  from  a  point  not  seen 
before,  seemingly  about  one-fourth  mile 
down  the  slope  of  the  mountain,  steaming 
quite  heavily  all  morning. 

Two  jets  of  steam;  one  from  the  crater  and  one 
from  the  north  crater — narrow  column  ris¬ 
ing  several  thousand  feet. 

Steamed  quite  heavily  all  day  from  north 
crater. 

Charles  Yori,  at  Drakesbad,  heard  rumbling 
noises  in  the  direction  of  Lassen  Peak. 
Small  eruption.  Clouds  rise  several  thousand 
feet.  Column  narrow  like  smokestack,  and 
extends  far  into  southern  sky. 

Steamed  all  day  from  the  north  crater  and  all 
afternoon  from  both  craters. 

O — “Eruption  from  north  crater  accompanied 
by  rumblings  distinctly  heard  at  Chester. 
Cloud  very  dark  colored  at  beginning,  getting 
lighter  in  about  20  minutes.  Duration  about  3 
hours,  height  10,000  feet.” 

D — “Lasting  one-half  hour.  East  side  new 
crater.” 

Lassen  was  white  with  the  new  snow  last  night, 
and  quite  a  cloud  of  steam  rising  from  new 
crater.  By  8  p.m.  it  was  obscured  by  fog  or 
cloud  until  afternoon,  when  it  cleared.  The 
snow  was  covered  with  ashes  and  quite  a 
cloud  of  steam  rising  from  new  crater. 

Lassen  steamed  very  heavy  all  forenoon  and 
until  about  2  p.m.  Heavy  cloud  of  steam 
hanging  over  the  mountain  for  2  hours 
about  midday. 

Lassen  steamed  quite  heavy  for  2  or  3  hours  in 
afternoon,  from  north  crater. 

Erupted  from  southeast.  Smoke — north. 
Heavy. 

Black  Smoke.  Smoke — north. 


180 


No. 

Eruption. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

IQI5 

M  inutes 

114 . 

F... . 

Jan. 

17 

6h30m  a.m. 

Unknown. 

Medium. 

115 . 

0.... 

li 

17 

8h  a.m. 

15  or  20  minutes. 

The  first  eruption  of  Lassen  Peak  seen  from 

Chester  this  month  occurred  at  8  a.  m.  from 
center  of  mountain.  Duration  15  or  20  min¬ 
utes.  Did  not  rise  to  any  great  height  but 
drifted  to  southwest  in  quite  a  heavy  cloud. 

116 . 

F.... 

ti 

18 

6h  a.m. 

Unknown. 

Medium. 

117 . 

0.... 

a 

18 

8h  a.m. 

Small  eruption  at  8  a.m.  from  center. 

Quite  a  heavy  eruption;  height  5,000  feet  dura- 

118 . 

0 .... 

u 

18 

lh15m  p.m. 

1  hour. 

tion  1  hour,  steaming  quite  a  bit  all  after¬ 
noon.  Cloud  drifting  clear  across  the  western 

sky. 

119 . 

F.... 

it 

19 

5h  p.m. 

Short. 

Slight. 

120  . 

D  . 

u 

21 

6h30m  a.m. 

1  hour. 

Went  about  1,000  feet.  Smoke — north. 

Cloud  not  rising  above  top  of  mountain  but 
drifting  west  or  southwest. 

121 . 

0 . 

a 

21 

8h10m  a.m. 

122 . 

F.... 

u 

22 

6h  a.m. 

Several  hours. 

Heavy. 

123 . 

().... 

it 

23 

6h  a.m. 

20  minutes  to 

Two  eruptions,  one  about  6  a.m.,  only  the  cloud 

F2  hour. 

seen  at  6:30;  cloud  drifted  in  N.E.  direction. 
This  eruption  was  of  medium  size,  duration 
was  from  20  minutes  to  one-half  hour. 

124 . 

F,  0,  D  .. 

a 

23 

9h15m  a.m. 

0,  D  reports  one 

F— “Medium.” 

hour,  F  reports  sev- 

0 — “Quite  heavy,  duration  about  1  hour. 

eral  hours. 

Cloud  went  several  thousand  feet  high,  drifted 
N.E.  The  rumbling  was  plainly  heard  at 
Drakesbad  and  Warner  Valley,  northeast  of 
Chester.” 

D — “Large  volume  of  smoke  lasting  1  hour.” 

Smoke — southeast. 

125 . 

F... . 

u 

25 

10h20m  a.m. 

Several  hours. 

Medium. 

126 . 

0 .  .  . 

a 

26 

12h10m  a.m. 

Loud  rumbling  noise  heard  in  direction  of  Las- 

sen  Peak,  12.10  a.m.  It  being  cloudy  no 
eruption  could  be  seen. 

127 . 

D  .  . 

u 

26 

10h25m  a.m. 

Black  smoke.  Smoke — north. 

128 . 

D.  .  . 

a 

26 

2h40m  p.m. 

Black  smoke. 

129 . 

F...  . 

Feb. 

5 

Late  in 

Unknown. 

Unknown.  Snow  darkened. 

afternoon. 

130 . 

F.... 

u 

6 

Earlv 

Unknown. 

Unknown. 

morning. 

131 . 

F,  0, 

D. 

it 

11 

6h50m  a.m. 

Several  hours. 

F — “Heavy.  Ash  cloud  reached  high  altitude.” 

0 — “  Eruption.” 

D — “  Smoked  all  a.m.” 

132 . 

F,  0.  D.  . 

a 

12 

About  5  a.m. 

Several  hours. 

F — “  Heavy.” 

0 — “  Eruption.” 

D — “Smoked  all  a.m.” 

133 . 

F,  D. 

a 

12 

12h55m  p.m. 

Several  hours. 

F — “Very  heavy  eruption  occurred.” 

D — “Large  eruption.  Thousands  of  feet  high.” 

134 . 

0... 

a 

20 

12h30m  a.m. 

Rumbling  heard  in  direction  of  Lassen 

Peak  at  12.30  a.m. 

135 . 

F...  . 

it 

26 

6h  a.m. 

Short. 

Medium. 

136 . 

0,  D. 

Mar. 

11 

7h40m  a.m. 

]/2  hour. 

O — “Medium  intensity,  duration  30  minutes.” 

D — “  Black  smoke.  Smoke — north.” 

137 . 

F...  . 

U 

12 

7h30m  a.m. 

Short. 

Medium.  Bumpass  Hell  in  an  eruptive  state 

just  previous  to  and  during  eruption.  Wit¬ 
nessed  by  Abbey  from  near  Brokeoff.  Cra¬ 
ter  appeared  from  Brokeoff  to  have  length¬ 
ened  considerably  in  direction  of  Lookout 
House. 

138 . 

0.... 

“ 

14 

Eruption  some  time  during  night.  Mountain 
covered  with  dust  this  morning  that  was 

white  last  night. 

139 . 

F.... 

a 

19 

5h  a.m. 

Could  not  be  deter- 

Very  heavy  eruption.  Falling  ash  caused  hazy 

mined. 

atmosphere  in  vicinity  of  mountain  for  great¬ 
er  portion  of  day.  Steam  could  be  seen  from 

F,  0, 

Red  Bluff  issuing  from  vents  on  side. 

140 . 

D. . 

a 

20 

5h30m  a.m. 

35  minutes. 

F — “One  of  the  heaviest  eruptions.  Condi- 

tions  similar  to  those  of  previous  day  pre¬ 
vailed.” 

181 


.  No- 

Eruption.- 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

1915 

Minutes 

140 . 

F.  0,  D .  . 

Mar. 

20 

5h30m  a.m. 

35  minutes. 

0 — "Heavy  eruption,  10,000  feet,  duration  35 
minutes.” 

D — “Largest  yet.  Crimson  clouds  of  smoke. 

As  sun  was  rising  reflections  were  beautiful 
and  wonderful.  Never  to  be  forgotten  by 
those  who  witnessed  the  grand  phenomenon. 
Black  smoke.  Ashes  fell  from  9  a.m.  to  10 
o’clock.  Ashes  reached  Paynes  Creek  and 
the  Black  Buttes.” 

141 . 

0 . 

U 

20 

6h30m  a.m. 

20  minutes. 

Medium  eruption,  duration  20  minutes. 

142 . 

F,  0 . 

U 

20 

7h50,n  a.m. 

Until  5  p.m. 

F — “  Medium.” 

0 — “Heavy  eruption  lasting  until  5  p.m.” 

143 . 

F . 

U 

21 

Short. 

Short. 

Medium. 

144 . 

0 . 

U 

21 

5h30m  a.m. 

143 . 

0.  D . 

U 

21 

10h15m  a.m. 

0 — 15  minutes. 

D — White  Smoke. 

D — 1  hour. 

146 . 

F,  0,  D. 

U 

21 

3h  p.m. 

F — Short. 

F — “  Medium.” 

0 — 2  hours. 

D — 1  hour. 

0 — “Column  rising  about  10,000  feet.” 

147 . 

() . 

u 

21 

9h30m  p.m. 

About  30  minutes. 

148 . 

I) . 

u 

21 

1 0h  p.m. 

Twenty-one  eruptions  at  night  about  10 
o’clock. 

140 . 

().  1) 

(i 

23 

0 — “Lassen  in  light  eruption  all  day.  Column 
not  rising  above  mountain,  but  rolling  over 

and  drifting  northward.” 

D — “Crater  smoked  all  dav.” 

150 . 

0 . 

Apr. 

4 

Nearly  all  forenoon. 

Light  eruption  nearly  all  forenoon.  Ob- 

scored  bv  clouds  after  11.30  a.m. 

151 . 

1) . 

U 

5 

6h  p.m. 

y2  hour. 

Smoke — south. 

152 . 

O . 

a 

6 

7h15m  a.m. 

2  hours. 

Medium  sized  eruption  at  7:15  a.m.  lasting 

two  hours. 

153 . 

O . 

u 

8 

Eruption  some  time  last  night  just  before  dark. 
The  east  side  of  Lassen  was  white  with  new 

snow  this  morning  at  7.30.  When  fog  cleared 
up  the  north  half  of  the  east  side  was  covered 
with  dust.  Ibis  evening  after  sunset  two 
columns  of  steam  were  rising  from  the  top  of 
Lassen  several  hundred  feet.  This  forenoon 
from  11  to  12  a  large  column  of  steam  was 
rising  from  Bumpass’. 

Charles  Yori  reports  quite  a  heavy  fall  of 
ash  at  Drakesbad,  sometime  during  the 
night  of  the  12-13th. 

F — “  Heavy.” 

154 . 

F,  0 . 

a 

15 

6h30m  p.m. 

F — Short. 

0 — Continued  un- 

Crater  visited  bv  Hampton  and  Kaul  Mar.  23, 

til  dark. 

1915.  Apparently  no  great  increase  in  size. 

O — “Heavy  column  rose  several  thousand  feet 

high,  continued  until  dark.” 

155 . 

0 . 

a 

16 

4h  a.m. 

Until  5.30  a.m. 

The  time  of  beginning  not  known,  only  esti- 

mated. 

156 . 

0,  I) . 

u 

16 

lh30m  p.m. 

0 — Most  of  the  af- 

O — “Cloud  drifting  this  way,  fumes  quite 

ternoon. 

strong  here,  no  dust  fell  to  amount  to  any¬ 
thing.” 

D — “  Resembled  horns.  Smoke — south.” 

157 . 

F,  0 . 

u 

16 

5h50m  p.m. 

F — Short. 

F — “  Medium.” 

0 — Continued 

O — “Cloud  drifting  southeast.” 

until  dark. 

158 . 

0 . 

« 

17 

A  small  amount  of  ash  fell  last  night. 

Medium. 

159 . 

F . 

(( 

26 

3h  p.m. 

Short. 

160 . 

F . 

u 

27 

3h30m  p.m. 

Unknown,  storming 

Heavv.  Volcanic  dust  fell  at  Manton. 

161 

0 . 

a 

27 

5h30m  p.m. 

30  minutes. 

Heavy,  duration  about  30  minutes. 

162.  . 

D . 

a 

30 

Ashes  fell  at  dusk  filling  hair  of  E.  Z.  Williams 
and  Alice  Dines  who  happened  to  be  work- 

ing  in  flower  garden.  Very  cloudy.  Eruption 
not  seen.  We  held  out  paper  and  caught  one- 
half  teaspoon  of  ashes  in  about  10  minutes. 
Ashes  fell  at  Cottonwood,  Shasta  County 

this  time.  Eruption  happened  during  a  storm. 

182 


174. 


F,  0,  D. 


22 


22 


,  No: 
Eruption. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

IQ  IS 

Minutes 

163 . 

O . 

May 

2 

Eruption  in  morning.  l  ime  of  beginning  not 
known.  Seen  at  5:30  a.m. 

164 . 

O . 

U 

3 

Eruption  first  seen  at  1  p.m.  and  at  intervals 
all  afternoon  until  7  p.m.,  when  it  was  cov- 

ered  by  cloud.  Was  cloudy  all  afternoon 
hut  cleared  up  enough  to  see  the  mountain 
several  times,  and  every  time  it  was  in  erup- 

tion. 

165 . 

O,  D . 

U 

4 

O — “Eruption  lasting  all  day.” 

I) — “  Black  smoke.  Cloudv  dav,  onlv  visible 

a  few  moments  at  3  p.m.  Smoke — south.” 

166 . 

O . 

u 

5 

In  eruption  all  day. 

In  eruption  all  day. 

F — “Reported  by  Ranger  from  Mineral.” 

167 . 

O . 

u 

6 

168 . 

F,  O . 

u 

7 

During 

Unknown,  storming. 

morning. 

O — “In  eruption  all  day.” 

169 . 

() . 

a 

13 

8h30m  a. m. 

Lassen  in  eruption  at  8.30  a.m.,  was  visible  only 
for  a  short  time,  cloudv.  Phis  was  the  first 

time  that  Lassen  had  been  seen  since  the  7th. 
Cloudv  all  the  time. 

170 . 

1) . 

u 

14 

2h40m  p.m. 

New  crater.  Large  eruption.  Smoke — east. 
Large  crater  first  visible  from  here  9  a.m. 

Fire  seen  for  first  time  by  8  persons.  I 
telephoned  to  all  having  phones  so  hundreds 
saw  the  fire,  which  lasted  all  night  and  was 
seen  just  before  daybreak  at  intervals  of  15 
minutes,  L2  hour,  and  r  hours. 

171 

() . 

a 

15 

Light  seen  on  top  of  Lassen  at  2.30  a.m. 

Various  parties  on  all  sides  of  mountain  re¬ 
ported  glow  above  crater  on  clouds. 

172 . 

F . 

a 

17 

Evening. 

Unknown. 

173 . 

F,  O,  D .  . 

u 

19 

10h30"'  p.m. 

Lin  known. 

F — “First  indication  of  eruption  was  tremen- 

During 

morning. 

4h30m  p.m. 


Long.  In  eruption 
up  to  time  of  large 
eruption. 

About  an  hour. 


clous  flood  of  mud,  etc.,  down  Hat  Creek. 
Meadows  covered.” 

0 — “Lassen  seen  this  afternoon  the  first  time 
for  six  days.  Was  in  eruption  all  the  time  it 
was  visible.  After  dark  a  steady  glow  of 
light  was  seen  shining  on  cloud  of  smoke  for 
several  hours.” 

D — “Mountain  smoked  all  day.  Fire  lava 
seen  on  top  at  9  p.m.  A  few  days  previous 
to  this  a  change  was  noticed  in  mountain.  A 
black-like  wall  appeared  coming  in  middle 
crater  getting  higher  every  day.  It  looked 
from  here  wedge-shaped  and  was  seen  from 
north  to  south  of  crater  and  mountain.  Af¬ 
ter  this  it  spilled  over  on  west  side  and  still 
remains  there.” 

Abbey  reported  mountain  in  continual  erup¬ 
tion  all  morning. 

From  point  3  miles  distant,  mountain  ap¬ 
peared  flattened  on  top.  Abbey’s  report. 

F — “Terrific  eruption.  Incomparable  with  any 
former  eruption.  Evidences  of  ejecta  such  as 
hot  mud,  hot  rocks,  and  pumice.  Heated 
boulders  fired  drift  wood  several  miles  from 
crater.  Several  new  fissures  on  mountain 
side,  especially  on  north  and  east  slope.” 

O — “Lassen  seen  today  first  time  since  19th. 
Was  in  light  eruption  all  day.  At  4.45  p.m. 
there  was  an  eruption  by  far  the  heaviest 
ever  seen,  lasting  about  an  hour.  Column  of 
steam  reached  a  height  of  about  30,000  feet.” 

D — “Eruption  was  largest,  grandest  ever  seen. 
Went  1,000  feet  high.  Large  volume  of  smoke 
first  drifted  over  Manton  but  turned  and 
smoke  and  ashes  drifted  to  Nevada.  Many 
people  hitched  their  horses  preparing  to 
leave.  Among  those  who  were  ready  to  de¬ 
part  were:  Mrs.  Kate  Stull,  R.  L.  Pruden 
and  family,  E.  L.  Tulbright  and  family.” 

Note. — No  earthquakes  ever  felt  at  Manton. 


183 


,  No.- 

Eruption. 

Authority. 

Date. 

Time. 

Duration. 

175 . 

F.  O . 

IQI5 

May  30 

5h  8m  p.m. 

M  inutes 

40  minutes. 

176 . 

O . 

“  31 

5h15m  a.m. 

177 . 

F . 

“  31 

9h30m  a.m. 

30  minutes. 

178 . 

O . 

June  1 
“  10 

10*’30m  p.m. 

179 . 

F . 

During 

Unknown. 

180 . 

0 . 

“  12 

night. 

3h  p.m. 

181 

F . 

“  16 

8h30m  a.m. 

20  minutes. 

182 . 

F . 

“  16 

lh15m  p.m. 
3h  a.m. 

20  minutes. 

183 . 

D . 

“  20 

184 . 

F . 

“  23 

10h44m  a.m. 

20  minutes. 

185 . 

F . 

“  26 

4h10m  a.m. 

Short. 

186 . 

F . 

July  2 

9h20m  p.m. 

Of  long  duration. 

187 . 

F . 

“  3 

8h10m  p.m. 

20  minutes. 

188 . 

F . 

“  13 

9h40m  p.m. 

20  minutes. 

189 . 

F . 

“  27 

4h30m  a.m. 

1  hour. 

190 . 

F . 

“  28 

2h50m  p.m. 

Several  hours. 

191 . 

F . 

Aug.  6 

7h  a.m. 

Continued  until 

192 . 

F . 

“  8 

9h50m  a.m. 

midnight. 

All  dav. 

193 . 

F,  C  .... 

“  25 

5h25m  p.m. 

2  hours. 

194 . 

F,  O . 

“  27 

8h30m  a.m. 

F — 50  minutes. 

195 . 

F,  O . 

Sept  1 

7h25m  a.m. 

0 — 1  hour. 

30  minutes. 

196 . 

F . 

“  3 

9h  a.m. 

20  minutes. 

197 . 

F,  O . 

“  18 

9h  a.m. 

6  hours. 

198 . 

F,  O . 

“  20 

9h30in  a.m. 

35  minutes. 

199 . 

F,  O . 

“  23 

9h45m  a.m. 

35  minutes. 

200 . 

F,  O . 

“  26 

2h  5m  p.m. 

F — 45  minutes. 

Intensity  and  Remarks. 


F — “Ordinary  volume.  Steam  issued  from 
north  slope  of  peak  quite  heavily  laden  with 
ash.  Main  crater  full  of  boulders.  Floor  of 
crater  appears  shoved  upwards.” 

O — “Medium  sized  eruption  at  5.10  p.m.” 

Medium  sized  eruption  at  5.15  a.m. 

Medium.  Em.ssion  from  crater  on  north  slope. 
Main  crater  quiet. 

Heavy  eruption  at  10.30  p.m. 

Unknown.  Mountain  unusually  active  follow¬ 
ing  morning.  Heavy  volumes  steam  from 
crater  low  down  on  west  slope. 

Eruption  at  3  p.m.  Light  continued  until  dark. 

Note. — I  am  not  certain  that  anything  was 
seen  from  Chester  between  June  12  and  Aug. 
25,  1915.  On  the  night  of  July  13,  1915, 
ashes  fell  at  Drakesbad  so  that  we  could 
write  our  names  on  porch  railing  in  the  morn¬ 
ing.  A  small  puff  of  steam  seen  in  fore¬ 
noon  of  Aug.  8,  when  J.  M.  Howells  and  I 
went  up  Lassen  Peak.  Steam  drifted  north¬ 
east.  J.S.Diller. 

Medium. 

Medium. 

Was  an  eruption.  Two  distinct  shots  of  fire 
ascended  with  black  smoke.  I  was  just  re¬ 
turning  from  a  dance.  It  was  witnessed  by 
G.  D.  Cronemiller  and  my  cousin,  Otto  Daily. 

Medium.  Entirely  from  crater  on  north  slope. 

Medium.  Witnessed  and  reported  by  lookouts. 

Very  heavy.  Ash  clouds  of  unusual  density. 
Slight. 

Medium. 

Heavy.  Eruption  from  north  crater.  Bumpass 
Hell  and  other  hot  springs  unusually  active. 
Increased  volumes  of  steam  from  crater  on 
top. 

Heavy.  Eruption  from  north  crater.  Rum¬ 
blings  distinctly  heard  at  Big  Springs. 

Quake  felt  at  summit  of  BrokeofF  at  11  a.m. 
Direction  N.  and  S.  Heavy  eruption. 

Very  heavy  eruption. 

F — “Heavy.  Rumblings  heard  by  BrokeofF 

Mountain  lookout.  Altitude  12,870  feet. 
Huge  jagged  boulders  cover  location  of  for¬ 
mer  crater.” 

O — “Heavy  eruption  at  5.25  p.m.  lasting  2 
hours.  Altitude  10,000  feet.” 

F — “Medium.” 

O — "Medium  eruption  at  8.30  a.m.  Duration 
about  1  hour. 

F — “  Medium.  Altitude  3,630  feet.” 

0 — “Medium  eruption  at  7.30  a.m.  Duration 
30  minutes.” 

Slight. 

F — “Heavy.  Unusually  active  until  3,30  p.m. 
Rumblings  heard  by  BrokeofF  lookout. 
Steam  and  sulphur  fumes  constantly  being 
emitted  from  many  fissures.” 

O — “Heavy,  lasting  until  6  p.m.  Heavy  until 
noon;  light  the  remainder  of  time.” 

F— “  Heavy.” 

O — “Heavy  eruption.  Duration  30  minutes.” 

F— “  Medium.” 

O — “Medium.  Duration  35  minutes.” 

I' — “Slight.  Nearby  observers  state  boulders 
8  inches  in  diameter  hurled  about  100  feet. 


184 


No. 

Eruption, 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

1915 

Minutes 

200  .... 

F.  O . 

Sept!  26 

2h  5m  p.m. 

0 — 30  minutes. 

Lassen  has  developed  3  distinct  new  craters  on 
northwest  portion  of  mountain.  These  are 

located  on  summit  of  mountain  directly  west 
of  old  crater;  are  circular  in  shape,  and  are 
at  present  the  outlet  of  most  material  thrown 

out. 

0 — “Light  eruption.  Duration  about  30  min- 

utes.” 

201 

F,  O . 

“  27 

2h50m  p.m. 

20  minutes. 

F — “Medium.  Very  deep  rumblings  heard  by 
Brokeoff  lookout.” 

0 — “Medium.  Duration  about  20  minutes.” 

202 

0 . 

“  30 

5h  p.m. 

Light  eruption  at  5  p.m. 

Earthquake  felt  at  11  p.m.  two  shocks,  light, 
no  sounds. 

203 

0  ... 

Oct  2 

1  lh  p.m. 

204  .... 

0 . 

“  6 

12h30m  p.m. 
10h45m  a.m. 

About  20  minutes. 

Medium  eruption  at  12.30  p.m. 

F — “Medium.  Slight  fall  of  snow  on  Lassen 

205 . 

F,  0 . 

“  14 

F — 30  minutes. 

0 — All  day. 

October  13.  Prospect  Peak  lookout  reports 
the  eruption  issued  from  new  fissure  on  north 
slope.” 

0 — “Light  eruption  lasting  all  day.” 

206 . 

F,  O.  ... 

“  15 

2h45m  p.m. 

1  hour,  30  minutes. 

F — “Medium.  Rumblings  heard  bv  Prospect 

Peak  lookout.  Eruption  from  above-men¬ 
tioned  fissure.” 

0 — “Steaming  all  day  quite  heavily  at  times.” 

207 

O . 

“  16 

Steaming  all  day  quite  heavy  at  times. 

F — “Medium.  Rumblings  heard  by  Prospect 
Peak  lookout.  Also  heard  by  Harvey 

208 . 

F,  O . 

“  17 

10h45m  a.m. 

1  hour. 

Mountain  lookout.  Eruption  from  above 

mentioned  fissure.” 

0 — “Steaming  quite  heavy  from  daylight  until 

10.50  a.m.  when  there  was  quite  a  heavy 
eruption.  All  the  eruptions  from  the  14th 
to  the  1 7 th  (inclusive)  seemed  to  come  from 
a  new  fissure  on  the  north  slope.” 

209 

O . 

“  19 

V  isited  the  summit  of  Mt.  Lassen.  Pound  but 

few  changes  since  July  25,  date  of  last  visit. 
Visited  the  new  fissure  and  found  it  steam- 

mg  quite  heavy.  The  steam  was  quite  full 
of  dust  and  sand;  it  had  collected  around  the 

opening. 

210 

O . 

“  24 

2h  p.m. 

Light  eruption  at  2  p.m. 

O — “Medium  eruption  at  7.30  p.m.  Light 

211 . 

O,  D . 

“  25 

7h30m  p.m. 

0 — 30  minutes. 

D — 20  minutes. 

flashes  and  bombs  seen  shooting  from  the 
crater.” 

D — “Moonlight.  Very  prettv  in  moonlight. 

Smoke — north.” 

212 . 

F,  O . 

“  30 

7h30m  p.m. 

F — Unknown. 

F — “Heavy.  Glow  over  crater  and  luminous 

0 — 30  minutes. 

bodies  reported  seen  by  various  parties.” 

O — “Heavy  eruption  7.30  p.m.  Large  flashes 

of  light  and  bombs  shot  high  above  top  of 
mountain  lasting  4  or  5  minutes,  the  erup¬ 
tion  lasting  about  30  minutes.” 

213 . 

F . 

“  31 

11  HO*"  a.m. 

20  minutes. 

Heavy. 

214 . 

F . 

Nov.  1 

12h25m  p.m. 

Short. 

Slight. 

215 . 

F . 

“  10 

8h30m  a.m. 

Short. 

Medium. 

216 . 

O . 

“  13 

1  lh40m  a.m. 

About  40  minutes. 

Heavy  eruption.  The  cloud  from  this  eruption 
went  about  11,000  feet  high. 

“Note.— This  was  the  last  eruption  seen  from 

this  place  up  to  Dec.  31,  1915.” 

217 . 

F . 

“  22 

Early 

Mountain  in  erup- 

Reported  by  Manton  and  Shingletown  resi- 

morning. 

tion  all  day. 

dents.  No  particulars. 

218 . 

1) 

Dec.  25 

Mountain  smoked  at  5  p.m.  Smoke  drifted  to 
south. 

219 . 

D . 

“  29 

6h  a.m. 

F.ruption  about  6  a.m.  Smoke  west  to  south 
Smoked  all  dav.  Mountain  hid  bv  large 

volume  of  smoke  settling  down  on  it. 

Note. — No  record  of  eruptions  between  Dec.  29,  1915  and  Sept.  24,  1916. 


185 


No. 

Eruption. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

iqi6 

Minutes 

220  . 

D . 

Sept. 

Oct. 

24 

7k 

a.m. 

All  day. 

Steam  at  intervals. 

221 . 

D . 

4 

Between  6 

? 

Black  smoke,  heavy,  ascending  into  clouds. 

and  7 

a.m. 

22? . 

D . 

(C 

5 

5h35m 

p .  m . 

Small  eruption  of  white  steam. 

Largest  eruption  of  the  summer.  Smoke  settled 

223 . 

D . 

u 

16 

9h 

a.m. 

Entire  day. 

around  mountain. 

224 . 

D . 

u 

24 

6h 

p.m. 

1  hour. 

Very  largest  this  vear.  White  and  black  smoke 

drifted  south  over  Brokeoff  Mountain.  Sul¬ 
phur  fumes  reached  Manton  at  9  p.m. 

Smell  very  strong  like  sulphur  and  something 
rotten.  Smoke  went  thousands  of  feet  in 

the  air. 

225 . 

D . 

u 

25 

a.m. 

Steaming  quite  heavy  this  morning. 

Very  large  eruption.  Smoke  rolled  out  but 

226 . 

D,  0 . 

Nov. 

1 

4h 

p.m. 

Yz  hour. 

went  down  in  strong  wind  to  north. 

227 . 

0 . 

« 

2 

Steam  rising  at  intervals  all  day. 

Heavy. 

Heavy. 

Medium  (0);  white  steam  came  straight  up  (D) 
Steam,  heavily  all  dav  and  drift  south. 

228 . 

0 . 

a 

8 

9h 

a.m. 

229 . 

0 . 

a 

9 

4h40m 

p.m. 

230 . 

D,  0 . 

Dec. 

17 

4h30m 

n.m. 

231 . 

D,  0 . 

U 

20 

All  day. 

All  day. 

232  . 

D . 

U 

28 

7h 

a.m. 

53^2  hours. 

White  steam  came  in  great  volumes. 

D . 

igi7 

233 . 

Jan. 

« 

1 

All  day. 

All  day. 

IE2  hours 

White  steam. 

234 . 

D . 

3 

White  steam,  small  quantity. 

Medium. 

235  . 

0 . 

a 

15 

4h 

p.m. 

236 . 

D . 

a 

16 

3h30m 

p.m. 

1  hour. 

White  steam. 

237 . 

D,  0 . 

a 

17 

9h45m 

a.m. 

All  day. 

D — “Large  eruption  of  black  smoke.  Ashes 

fell  on  Brokeoff.  Rumblings  heard  15  miles 
at  Crookes.  None  heard  at  Manton.” 

0 — Medium  heavy  growing  lighter  to  little 

steaming  at  dark. 

238 . 

D . 

u 

18 

a.m. 

Strong  sulphur  at  Crookes’  place,  15  miles. 
Smoke  drifting  south. 

239 . 

D . 

u 

20 

4h20m 

p.m. 

1%  hours. 

240 . 

D,  0 . 

a 

30 

7h 

a.m. 

D — “Great  quantities  of  white  steam.” 

0 — “New  snow  covered  with  dust  on  N, 

Y  of  east  side  of  mountain.” 

241 . 

0 . 

Feb. 

1 

Another  night  eruption,  covering  entire  east 
side  of  mountain. 

242 . 

0,  D . 

a 

3 

7h 

a.m. 

All  day. 

O — “  Steamed  slightly.” 

D — “White  steam,  great  quantity  until  noon.” 

243 . 

0 . 

u 

18 

9h 

a.m. 

1  hour. 

Medium  heavv  cloud  went  several  thousand 

feet  high. 

0 . 

Mar. 

8 

2h 

a.m. 

Two  light  earthquake  shocks.  No  eruption. 

0 — “Steaming  quite  heavily  whenever  visible.” 

D — “Mountain  more  active.  Eruption  dur¬ 
ing  night  of  21st,  covering  snow  with  dust.” 

244 . 

0.  D . 

“  16-20 

D . 

a 

21 

245  .... 

D,  0 . 

u 

22 

llh30™ 

a.m. 

Y  hour. 

D — “Eruption  large.  Jet  black  smoke  drifts 
south.” 

O — “  Smoke  rose  3,000  feet.” 

246 . 

D,  0 . 

Apr. 

5 

2>'25,n 

p.m. 

Y  hour. 

D — “Largest  of  this  year.  Must  have  gone  up 

1,000  feet  before  black  smoke  drifted  south. 
Ashes  fell  to  south.” 

0 — “Clouds  go  several  thousand  feet  high. 

This  is  the  heaviest  eruption  I  have  seen 
since  big  one  Mav  22,  1915.” 

247 . 

D,  0 . 

U 

6 

8h15m 

a.m. 

3  hours. 

D — “  Black  smoke  drifted  south.  Ashes.” 

O — “  Continues  medium  about  30  minutes.” 

0 . 

U 

8 

llh30m 

a.m. 

One  slight  earthquake  shock. 

248 . 

D,  0 . 

u 

15 

6h 

a.m. 

1  hour. 

D — “Smoke  rises  thousands  of  feet  in  air.” 

O — “Medium.  Small  column  rising  several 

249 . 

0 . 

u 

18 

llh 

a.m. 

hour. 

thousand  feet.” 

250 

D . 

a 

19 

2h10m 

p.m. 

Smoke  went  up  into  clouds. 

Very  large.  Smoke  went  thousands  of  feet  in 
the  air. 

251 

D . 

May 

4 

7h10m 

a.m. 

252 . 

D . 

4 

lh 

p.m. 

2  hours. 

Very  large.  Smoke  went  thousands  of  feet 

in  the  air. 

186 


No. 

Authority. 

Date. 

Time. 

Duration. 

Intensity  and  Remarks. 

Eruption. 

1917 

M  inutes 

253 

D 

May 

4 

10h30m  p.m. 

Black  smoke  drifts  south.  Eruption  large,  half¬ 
way  down  mountain  side  as  big  eruption. 

254 

0 . 

« 

9 

6h45m  p.m. 
6h45m  a.m. 

30  minutes. 

Medium. 

255 . 

0 . 

u 

13 

30  minutes. 

Heavy.  Large  volume  of  dust  and  steam. 

256 . 

D,  0 . 

u 

18 

12h45m  p.m. 

6  hours. 

0 — “Very  heavy.  Clouds  rising  10,000  to 

12,000  feet,  accompanied  by  loud  rumblings 
lasting  until  darkness  obscured  view.” 

257  . 

0 . 

a 

19 

All  dav. 

0 — “Steaming  heavily  all  day — quite  large 

after  sundown.  Rumblings  heard  from  3 
to  5  p.m.” 

258 . 

D,  0 . 

u 

20 

6h  a.m. 

All  dav. 

0 — “  Steaming  all  day  quite  heavy.  Rumblings 

heard  during  afternoon.” 

259 . 

0 . 

u 

21 

10h  a.m. 

30  minutes. 

Medium. 

260 . 

D,  0 . 

u 

22 

7h20m  p.m. 

y2  hour. 

D — “Black  smoke  lasting  hour.” 

0 — “A  steady  glow  of  light  seen  on  summit 

at  9  to  10  p.m. 

261 

0 

a 

29 

Eruption  during  night.  Ashes  fell  at  Feather 
River  Meadows. 

262 . 

0 . 

u 

30 

6h15m  a.m. 

45  minutes. 

Heavy. 

263 . 

D,  0 . 

u 

31 

llh  a.m. 

1  hour. 

D — “Large.  Smoke  to  south.” 

0— “Heavy.” 

264 . 

0 . 

a 

31 

5h10,n  p.m. 

30  minutes. 

265 . 

0 . 

June 

1 

3h  p.m. 

30  minutes. 

Medium. 

266 . 

0 . 

U 

2 

10h  a.m. 

30  minutes. 

Heavy. 

267 

D 

U 

2 

lh20,n  p.m. 

Large.  Smoke  went  high  in  the  air. 

268 . 

0 . 

u 

3 

8h  a.m. 

30  minutes. 

Medium. 

269 

D 

a 

3 

lh30m  p.m. 

Black  smoke  went  high  in  the  air. 

270 

D 

i t 

3 

4h20m  p.m. 

Small  eruption — white  steam. 

Small  eruption — white  steam. 

271 . 

D,  0 . 

u 

3 

5h55m  p.m. 

15  minutes. 

272 . 

D . 

u 

3 

7h  7m  p.m. 

15  minutes. 

Small  column  high  in  air. 

273 . 

0 . 

a 

3 

8h20m  p.m. 

15  minutes. 

Small. 

274 . 

D,  0 . 

a 

4 

7h10m  a.m. 

40  minutes. 

D — “Large.  Black  smoke  thousands  of  feet  in 
*  )» 

275  . 

D,  0 . 

a 

4 

10h  a.m. 

20  minutes. 

0— “  Light.” 

276 . 

D . 

a 

4 

lh40m  p.m. 

30  minutes. 

Smoke  high  in  air. 

277  . 

D,  0 . 

u 

4 

6h50m  p.m. 

30  minutes. 

0— “  Heavy.” 

278  . 

0 . 

u 

6 

7h40in  a.m. 

1  hour. 

Heavy  smoke  rising  about  10,000  feet. 

279 . 

D . 

(C 

6 

7h  a.m. 

1  hour. 

Black  smoke  large. 

280 . 

D . 

u 

6 

lh  p.m. 

20  minutes. 

281 . 

D,  0 . 

a 

8 

2h30m  p.m. 

2  hours. 

D — "Terrible  eruption.  Smoke  went  north.” 

0 — “Heavy.  Four  hours.” 

28? . 

D . 

u 

8 

6h40m  p.m. 

15  minutes. 

Small,  white  eruption. 

283 . 

0 . 

u 

10 

lh  p.m. 

All  afternoon. 

Medium. 

284 . 

D,  0 . 

a 

21 

2h20m  p.m. 

1  hour. 

Light.  Smoke  went  north. 

285 

0. . . . 

u 

27 

6h15m  a.m. 

Medium. 

286 . 

D,  0 . 

a 

29 

3h  p.m. 

1  hour. 

D — “Large.  Black  smoke  drifted  north  1  hour.” 

0 — “  Medium.” 

1918 

No  eruptions  reported  for  1918. 

292 . 

D . 

1919 

Jan.  9 

3h  p.m. 

1  hour. 

Small  smoke — evaporated  short  distance  above 

mountain. 

293 . 

D . 

(( 

10 

1  hour. 

Small  smoke — evaporated  short  distance  above 

mountain. 

294 . 

D . 

Apr. 

8 

5h30m  a.m. 

Black  smoke  drifted  south  until  7  a.m. 

295 

D.  .  . 

« 

9 

6h  a.m. 

Small  quantity  of  white  smoke  drifting  south. 

1920 

296 . 

D . 

Oct. 

24 

8h  a.m. 

10  hours. 

Quantity  of  black  smoke  rising  rapidly  and 

drifting  south. 

297 . 

D . 

Oct. 

30 

7h  a.m. 

12  hours. 

Small  smoke  arising  slowly  disappeared  at  sum- 

mit  of  peak. 

1921 

298 . 

D . 

Feb. 

7 

7h  a.m. 

5  hours. 

Great  clouds  of  white  steam  issuing  from 

1 

eastern  fissures. 

Note. 

— The  newspapers 

of  Red  Bluff  and  Redding  in  the  Sacramento  Valiev  have  reported  a  number  of  eruptions 

during  the  years  since 

1917  that  appear  to  have  been  cloud  banners  about  Lassen  Peak  rather  than  eruptions  of  steam. 

The  latest  eruption  seen  by  G.  W.  Olsen,  the  observer  at  Chester,  was  Aug.  23,  1917. 

INDEX. 


Acid  sulphates,  in  salt  incrustations,  1 1 7  (table), 
146. 

Acid,  sulphuric  in  hot  spring  waters,  113. 

Acid,  sulphuric  in  porous  ground,  140,  142,  144, 

145- 

Adams,  L.  H.,  174. 

Algae  in  hot  spring  waters,  89,  90,  99. 

Alignment  of  hot  spring  groups,  87. 

Aluminum  salts: 

Discussion  of  occurrence,  144. 

In  hot  spring  waters,  no,  in,  112  (table  3). 
In  incrustations,  117  (table  4). 

Minerals  formed  by,  118. 

Alunite,  occurrence  in  hot  springs,  120. 

Alunite,  deposits  in  hot  spring  areas,  141. 
Alunogen,  occurrence  in  salt  incrustations,  118. 
Ammonium  salts,  in  hot  spring  waters,  in,  112. 
Ammonium  salts,  in  incrustations,  117  (table). 
Analyses  of  lavas,  37,  39,  41,  48. 

Andesite,  occurrence,  1,  37,  41,  42,  44,  51,  73. 
Ash : 

Clouds,  3 1 

Composition,  40,  41,  42. 

Inclusion,  53. 

Aurousseau,  M.,  1,  36,  40,  48,  81. 

Basalt,  Occurrence,  36,  37,  81. 

Biotite: 

Effect  of  heating,  43,  49,  50. 

In  bombs,  71. 

Occurrence,  42. 

Significance,  44,  49,  50. 

Boiling  Lake  (Lake  Tartarus),  5. 

Elevation,  88. 

Salt  incrustations,  114,  117. 

Seasonal  thermal  changes,  155,  156. 
Sketch-map,  114. 

Spring  waters,  hi. 

Temperatures,  105. 

Bombs,  68,  69,  71. 

Boric  acid,  amount  in  hot  spring  waters,  in,  112. 
Boric  acid,  determination  of,  no. 

Boulders,  Transported  by  Mud  Elow,  22. 
Bowen,  N.  L.,  81. 

Bread-crust  surfaces,  45,  47,  51,  69,  70. 

Breccia,  52,  68,  71. 

Bumpass  Hell,  5. 

Elevation,  94. 

Maximum  temperatures,  96. 

Rock  alteration  by  fumarole  gases,  94 
Salt  incrustations,  114,  117. 


Bumpass  Hell. — Cont. 

Sketch-map,  95. 

Small  basalt  area,  87. 

Spring  waters,  1 12. 

Temperatures,  107. 

Bunsen,  R.  W.,  87,  126,  134,  139,  146,  163,  167. 

Capillarity,  influence  on  penetration  of  water 
into  deep-seated  rocks,  174. 

Causes  of  volcanic  activity,  31,  72,  76,  83,  84. 
Chapin,  W.  H.,  1 10. 

Chemical  Composition  of  Lavas,  37,  39,  41,  48, 

.77- 

Chemical  processes,  as  source  of  heat  in  hot 
springs,  151. 

Chlorides : 

Fumarole  product  in  the  crater  of  Lassen 
Peak,  146. 

General  absence  of,  .11  the  hot  spring  waters 
1 10. 

Presence  of,  in  Moigan’s  Springs,  100. 
Christensen,  126. 

Cinder  Cone,  I,  3,  36,  43,  61. 

Clarke,  F.  W.,  47,  137,  145,  147. 

Conclusion,  175. 

Crenshaw,  J.  L.,  137,  138. 

Culmination  of  activity,  14,  16,  33,  75. 

Dacite,  occurrence,  1,  3,  37,  41,  42,  51,  71,  73. 
Dana,  E.  S.,  1 18. 

Day,  P.  C.,  154. 

Debus,  H.,  145. 

Devil’s  Kitchen,  5. 

Elevation,  91. 

Heat  carried  away  by  Warner  Creek,  154. 
Occurrence  of  recent  pyrite,  122. 

Pyrite  mirrors  on  pools,  122. 

Recent  changes  in  thermal  activity,  1 58— 
1 6 1 . 

Salt  incrustations,  114. 

Seasonal  changes  in  thermal  activity,  155, 

156- 

Sketch-map,  92. 

Spring  waters  of,  hi. 

Temperatures,  106,  107. 

Thermal  activity  in  different  years,  156-157. 
Deville,  Ch.  Ste-Claire,  47,  139. 

Differentiation  of  Lassen  lavas,  1,  39,  80. 

Diller,  J.  S.,  1,  2,  3,  4,  6,  10,  n,  12,  32,  36,  41,  61, 
62,  63,  64,  65,  73,  81,  87,  88,  108,  1 19,  120, 
Hi- 


187 


188 


Din  es,  Alice,  Postmistress  Manton,  15,  17,  33,  34, 
63,  176. 

Drakesbad — see  Drake’s  Springs. 

Drake’s  Springs: 

Absence  of  salt  incrustations,  1 1 3 . 

Elevation,  90. 

Prevalence  of  algae,  90. 

Sifford’s  camp,  91. 

Spring  water,  1 12. 

Temperatures,  106. 

Use  of  water  for  bathing,  91. 

Dumas,  J.  B.,  140. 

Earthquakes,  Effect  of,  82. 

Eaton,  F.  M.,  1 13,  161. 

Ejecta: 

Character  of,  31. 

Evidence  of  Fluid,  16,  17,  18. 

Temperature  of,  8,  12,  13. 

Volcanic  bombs  and  breccia,  68,  69,  70,  71. 
Elevation,  Lassen  Peak,  3. 

Eruptions,  periodicity  of,  9,  31,  34,  82. 

Explosive  activity,  3,  11,  28,  31,  67,  75. 
Explosion  craters,  8,  28,  29,  31,  33. 
Eyewitnesses,  dependence  upon,  13,  16. 

Faults,  relation  to  hot  springs,  87,  150. 

Fenner,  C.  N.,  43. 

Ferric  ratio,  44,  48. 

Field  work,  86,  104. 

Fisher,  Osmond,  174. 

Fissures,  crater,  3,  8,  31,  42,  63,  64,  65,  67,  81. 
Flow,  lava: 

Discussion  of,  59,  61,  62,  75. 

Evidence  of,  34,  50,  52. 

Reports  of,  12,  16,  17. 

Forest  Service,  3,  6,  8,  12,  13,  14. 

Fumaroles,  7,  72. 

Action  on  lavas,  142-147. 

Expectionally  hot  one  Bumpass  Hell,  96. 
Hydrochloric  acid  within  Lassen  crater,  146. 
Occurrence,  88,  93,  94. 

Salts  from  fumarole  action,  143  e t.  seq. 
Seasonal  variation  in  volume  of  steam,  155. 
Significance  at  temperature  of  boiling  water, 
,  US- 

Sulphur  dioxide  along  eastern  rim  of  crater, 

US- 

Upper  limit  to  magmatic  water,  173. 
Fumes,  11,  12,  16,  74. 

Gas  content  of  conduit  lava,  46,  47,  51,  52. 
Gases,  volcanic: 

Analyses  of,  124  et.  seq. 

Collection  of,  123,  124. 

Composition  of,  130-136. 

Comparison  with  other  localities,  134,  135. 


Gases  volcanic — Cont. 

Former  distribution,  Bumpass  Hell,  94,  142. 
Hydrochloric  acid  within  crater,  146,  147. 
Hydrogen  sulphide,  method  of  determina¬ 
tion,  124,  128. 

Hydrogen  sulphide,  oxidation  to  free  sul¬ 
phur,  139,  140. 

Hydrogen  sulphide,  oxidation  to  sulphuric 
acid,  140. 

Hydrogen  sulphide,  variation  in  springs, 
134- 

Occurrence  in  hot  springs,  150. 

Oxygen  not  an  original  constituent,  130  et. 
135,  136.  _ 

Significance  of  inert  constituents  in  hot 
springs,  134,  135. 

Soluble  gases  from  Lassen  crater,  145. 
Source  of,  150. 

Sulphur  dioxide  on  crater  rim,  145. 

Sulphur  dioxide,  relation  to  volcanic  ac¬ 
tivity,  146. 

Geological  Relations,  1. 

Geological  Survey,  36. 

Geyser,  5. 

Elevation,  88. 

Temperatures,  103. 

Variable  activity,  88,  153. 

Geyser  at  Morgan’s  Springs,  99,  101. 

Glass: 

Glass  content  of  conduit  lava,  43,  32. 

Glass  111  bread-crust  surfaces,  45. 

Hague,  Arnold,  1,  36,  39,  44,  118,  134,  160,  163, 
167. 

Halotnchite  in  soft  incrustations,  118. 
Hampton,  E.  N.,  14. 

Harker,  A.,  36,  37, 

Heat: 

Chemical  processes  as  source  of  heat,  1 5 1— 

^53- 

Conduction  through  rock,  171. 

From  change  of  state  in  surface  water,  172. 
Heat  derived  from  magma,  133. 

Loss  from  Devil’s  Kitchen,  153. 
Radioactivity  as  source  of  heat,  130. 

Source  of  in  hot  springs,  130. 

Transfer  by  magmatic  steam,  170. 
Hillebrand,  W.  F.,  40. 

Holway,  R.  S.,  12,  18,  19,  20,  62. 

Horizontal  Blasts: 

Cause  of  mud  flow,  34. 

Effects,  19,  21,  25,  66. 

Prostration  of  trees,  23. 

Sand  blasting  effects,  24. 

Source,  67. 

Temperature,  56,  58. 


189 


Hot  springs — see  Springs. 

Hydrochloric  acid — see  Gases  volcanic. 
Hydrogen — see  Gases  volcanic. 

Hydrogen  sulphide — see  Gases  volcanic. 

Iddings,  J.  P.,  i,  36,  39,  44. 

Iron,  state  of  oxidation  in  hot  waters,  112,  113. 

Jaggar,  T.  A.,  experiments  at  Kilauea,  171,  172. 
Jillson,  W.  R.,  1. 

Johnston,  J.,  137,  174. 

Juvenile  gases,  52,  60,  65,  74,  82. 

Kaolin,  genesis,  141. 

Kaolin,  occurrence  in  hot  spring  sediments,  119. 
Kemp,  J.  F.,  174. 

Lacroix,  A.,  73- 
Larsen,  E.,  137. 

Lassen  Peak: 

Hydrochloric  acid,  146,  147. 

Hydrogen  sulphide,  145. 

Pentathionates  in  salts,  115,  145,  146. 

Salts  from  fumarole  action,  144. 

Soluble  gases,  145. 

Sulphur  dioxide,  145. 

Lassen  volcanic  ridge,  relation  to  hot  springs,  87. 
Lavas: 

Classification,  36,  37. 

Composition,  137. 

Decomposition  by  gases  and  hot  waters,  140 
et.  seq. 

Lava  Flow — see  Flow,  lava. 

Lindgren,  W.,  141 . 

Loomis,  B.  F.,  15,  19,  25,  26,  33,  34,  63. 
Magma: 

Crystallization  of,  77,  79. 

Gas  pressure  in,  80,  81. 

Relation  to,  76,  83. 

Magmatic  water — see  Water. 

Maps: 

Boiling  Lake,  1 14. 

Bumpass  Hell,  95- 
Devil’s  Kitchen,  92. 

Lassen  Peak  Region,  55. 

Sketch,  preparation,  104. 

Marcasite,  absence  from  Lassen  Springs,  138. 
McLaurin,  J.  S.,  145. 

Merwin,  H.  E.,  49,  71,  113,  118,  119,  120,  144. 
Milford,  G.  R.,  16,  18,  59,  61. 

Mill  Creek  Springs,  98. 

Elevation,  107. 

Temperatures,  107. 

Mont  Pelee,  3,  10,  34,  51,  72,  73,  80. 

Morey,  G.  W.,  76,  164. 

Moore,  R.  B.,  150. 


Morgan’s  Springs,  5. 

Algae,  99. 

Sinter,  99. 

Temperatures,  100. 

Mud  flows: 

Causes,  25,  26,  34,  58,  75. 

Composition,  40,  42. 

Effects,  19,  22. 

Origin,  20,  21. 

Mud  pots,  89,  91,  94,  96,  101. 

Collection  of  water  from,  109. 

Collection  of  gases  from,  124. 

Mud  volcanoes: 

Formation,  103. 

Relation  to  fumaroles,  155. 

Relation  to  mud  pots,  103. 

Nasini,  R.,  134. 

Norms  of  Lassen  lavas,  40. 

Opal  m  hot  spring  sediments,  1 19. 

Opal,  last  product  of  rock  decomposition,  142. 

Park,  James,  138,  139,  163,  167,  168. 
Pentathionate — see  Salt  incrustations. 
Periodicity  of  eruptions,  9,  31,  34,  82. 

Perret,  F.  A.,  47. 

Phillips,  F.  C.,  135. 

Pickermgite,  118. 

Plug,  upheaval  of,  33,  42,  57,  62,  64,  66. 
Posmak,  E.,  144. 

Precipitation  (ram  and  snow)  in  hot  spring  dis¬ 
tricts,  134,  155. 

Pressure,  gas  in  magma,  80,  81. 

Prestwich,  Joseph,  6. 

Pumiceous  andesite,  42,  43,  44,  47,  52,  68. 
Pyrite: 

In  black  and  gray  muds,  122,  123. 

Recent  occurrence,  93,  121,  122. 

Recent,  observed  crystal  forms,  137. 

Scums  and  mirrors  on  pools,  122. 

Quartz  basalt,  occurrence,  36,  37,  61. 

Radioactivity  as  source  of  heat  in  hot  springs, 

Go- 

Rhyolite,  occurrence,  1,  37,  41. 

Richtofen,  F.  von.,  1. 

Sabeck,  A.,  141. 

Salt  incrustations,  113-115. 

Chemical  analyses,  117. 

Microscopic  analyses,  118. 

Formation  by  waters  and  gases,  143,  144. 
Mineral  constituents,  118. 

Pentathionates  in,  115-118. 

Relation  to  dryness  oi  ground,  157. 


190 


Schlundt,  H  ,  150. 

Schneider,  F.,  163. 

Seasonal  changes,  influence  on  hot  springs,  155. 
Sediments  in  hot  springs,  119. 

Shepherd,  E.  S.,  40,  46,  49,  53,  60,  62,  125,  145. 
Sinter  at  Morgan’s  Springs,  99. 

Snow,  participation  of,  20,  21,  26,  30,  31,  32,  33, 
56,  58.  84. 

Spaulding,  W.  H.,  observations,  20,  63. 
Spouting  springs,  172. 

Springs  hot: 

Changes  in  volume  and  temperature,  155. 
Composition,  110-112. 

Fluctuations  in  composition,  1 6 1 ,  162. 
Methods  of  analysis,  109,  no. 

Presence  of  magmatic  water,  162. 

Relation  of  acid  to  alkaline,  165—169. 
Relation  to  fumaroles,  164,  173. 

Source  of  heat,  see  heat. 

Source  of  water,  154  et  seq. 

Spouting,  100. 

Temperatures,  105-108. 

Types,  100. 

Variations  in  temperature  of,  173. 

Various  groups,  87. 

Steam — see  Water. 

Steam  cloud,  height  of,  10,  31,  34. 

Stokes,  H.  N.,  139. 

Subsidence,  26,  34. 

Sulphates  in  waters,  no. 

Sulphur: 

Formation  from  H2S ,  140. 

Occurrence,  93,  94,  97,  99,  120. 

Oxidation  to  H2SO4,  140. 

With  pentathionate,  1 1 7  (footnote). 
Sulphuric  acid: 

Action  on  kaolin,  144. 

Action  on  lavas,  140. 

Formation,  138-140,  146. 

In  hot  spring  waters,  113. 

In  salt  incrustations,  117,  144. 

Surface  water — see  Water,  surface. 

Supan’s  Springs,  5,  96. 

Alumte  at,  141. 

Sulphur  deposit,  97. 

Temperatures,  97,  108. 


Tartarus  Lake — See  Boiling  Lake. 

Temperature  of  Plot  Springs,  104-108. 

Influence  of  barometric  pressure,  104. 
Temperatures  Volcano: 

Evidence  of  high  temperatures,  74. 

Flow  temperature  of  andesite,  50. 
Horizontal  blasts,  54. 

Indications  from  bombs,  70,  71. 

Summit  temperature  during  activity,  59,  62, 
64. 

Upheaved  plug,  49,  52. 

Thermal  activity: 

Cause  of  variations,  160,  161. 

Recent  changes  in  Devil’s  Kitchen,  158-161. 
Seasonal  changes,  155. 

Variations  in  different  years,  156,  157. 
Thionates,  characteristic  reactions,  116. 
Thorkelson,  J.,  126,  135,  150,  163,  171. 

Timber,  destroyed,  22,  23. 

Trees,  prostrated,  23,  34,  67. 

Trees,  sand-blasted,  24. 

Undercooled  magma,  83. 

Upheaval  of  volcano  plug,  33,  42,  57,  62,  64,  66. 

Viscous  movement,  42,  43,  61,  62,  65,  76. 
Volcanic  gases — see  Gases. 

Wackenroder,  H.,  145. 

Waring,  G.  A.,  99,  162. 

Washington,  H.  S.,  4,  36,  43. 

Water  content  of  lava,  37,  44,  45,  76,  82. 

Water,  magmatic: 

Limits  in  fumaroles,  173. 

Limits  in  hot  springs,  170,  171. 

Most  important  of  volcanic  gases,  136. 
Source  of  heat  in  hot  springs,  170. 

Water,  surface: 

Agent  in  transfer  of  heat,  172. 

Penetration  into  deep-seated  rocks,  174. 
Volume  and  temperature  in  springs,  155- 
157- 

Wheeler,  W.  C.,  1 19. 

Yori,  Charley,  13,  19,  59. 

Zies,  E.  G.,  no,  129,  138,  146. 


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